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                                 UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                   FORM N-Q

                   QUARTERLY SCHEDULE OF PORTFOLIO HOLDINGS
    OF REGISTERED MANAGEMENT INVESTMENT COMPANY



  Investment Company Act file number 811-01466


                            Pioneer Fund
               (Exact name of registrant as specified in charter)


                       60 State Street, Boston, MA 02109
              (Address of principal executive offices) (ZIP code)


            Terrence J. Cullen, Pioneer Investment Management, Inc.,
                       60 State Street, Boston, MA 02109
                    (Name and address of agent for service)


Registrant's telephone number, including area code:  (617) 742-7825


Date of fiscal year end:  December 31

Date of reporting period:  March 31, 2011

Form N-Q is to be used by management investment companies, other than small
business investment companies registered on Form N-5 (239.24 and 274.5 of this
chapter), to file reports with the Commission, not later than 60 days after
close of the first and third fiscal quarters, pursuant to Rule 30b1-5 under
the Investment Company Act of 1940 (17 CFR 270.30b1-5).  The Commission may
use the information provided on Form N-Q in its regulatory, disclosure review,
inspection, and policymaking roles.

A registrant is required to disclose the information specified by Form N-Q,
and the Commission will make this information public. A registrant is not
required to respond to the collection of information contained in Form N-Q
unless the Form displays a currently valid Office of Management and Budget
("OMB") control number. Please direct comments concerning the accuracy of the
information collection burden estimate and any suggestions for reducing the
burden to Secretary, Securities and Exchange Commission, 450 Fifth Street, NW,
Washington, DC 20549-0609.  The OMB has reviewed this collection of information
under the clearance requirements of 44 U.S.C. ss. 3507.


<PAGE>


ITEM 1. Schedule of Investments.


       
Pioneer Fund
   
       
Schedule of Investments  3/31/11 (unaudited)
   
 
Shares
       
Value
       
COMMON STOCKS - 99.8 %
   
       
Energy - 13.3 %
   
       
Coal & Consumable Fuels - 0.4 %
   
 
492,831
   
Consol Energy, Inc.
$
26,430,527
       
Integrated Oil & Gas - 7.8 %
   
 
2,129,710
   
Chevron Corp.
$
228,794,745
 
1,225,769
   
ConocoPhillips, Inc.
 
97,889,912
 
997,321
   
Exxon Mobil Corp.
 
83,904,616
 
818,099
   
Hess Corp.
 
69,710,216
 
1,429,209
   
Marathon Oil Corp.
 
76,191,132
         
$
556,490,621
       
Oil & Gas Drilling - 1.0 %
   
 
783,948
   
Ensco Plc (b)
$
45,343,552
 
344,982
   
Helmerich & Payne, Inc. (b)
 
23,696,814
         
$
69,040,366
       
Oil & Gas Equipment & Services - 1.5 %
   
 
985,662
   
McDermott International, Inc. *
$
25,025,958
 
887,096
   
Schlumberger, Ltd.
 
82,730,573
         
$
107,756,531
       
Oil & Gas Exploration & Production - 2.6 %
   
 
1,109,364
   
Apache Corp.
$
145,237,935
 
458,333
   
Devon Energy Corp.
 
42,061,219
         
$
187,299,154
       
Total Energy
$
947,017,199
       
Materials - 6.2 %
   
       
Aluminum - 0.7 %
   
 
3,012,994
   
Alcoa, Inc. (b)
$
53,179,344
       
Diversified Chemical - 0.8 %
   
 
1,074,838
   
E.I. du Pont de Nemours & Co.
$
59,083,845
       
Diversified Metals & Mining - 3.4 %
   
 
1,261,647
   
Freeport-McMoRan Copper & Gold, Inc. (Class B)
$
70,084,491
 
2,405,015
   
Rio Tinto Plc
 
169,200,181
         
$
239,284,672
       
Industrial Gases - 0.7 %
   
 
741,415
   
Airgas, Inc. (b)
$
49,244,784
       
Specialty Chemicals - 0.6 %
   
 
776,011
   
Ecolab, Inc.
$
39,592,081
       
Total Materials
$
440,384,726
       
Capital Goods - 10.9 %
   
       
Aerospace & Defense - 2.7 %
   
 
909,273
   
General Dynamics Corp.
$
69,613,941
 
462,571
   
Lockheed Martin Corp.
 
37,190,708
 
977,776
   
United Technologies Corp. (b)
 
82,768,738
         
$
189,573,387
       
Construction & Farm Machinery & Heavy Trucks - 4.3 %
   
 
654,874
   
Caterpillar, Inc.
$
72,920,220
 
888,968
   
Deere & Co.
 
86,132,110
 
2,801,990
   
PACCAR, Inc.
 
146,684,177
         
$
305,736,507
       
Electrical Component & Equipment - 1.6 %
   
 
1,104,532
   
Emerson Electric Co.
$
64,537,805
 
546,155
   
Rockwell International Corp. (b)
 
51,693,571
         
$
116,231,376
       
Industrial Conglomerates - 1.5 %
   
 
655,662
   
3M Co.
$
61,304,397
 
2,316,305
   
General Electric Co.
 
46,441,915
         
$
107,746,312
       
Industrial Machinery - 0.8 %
   
 
463,261
   
Illinois Tool Works, Inc.
$
24,886,381
 
315,362
   
Parker Hannifin Corp.
 
29,858,474
         
$
54,744,855
       
Total Capital Goods
$
774,032,437
       
Transportation - 4.6 %
   
       
Railroads - 4.6 %
   
 
1,281,360
   
Canadian National Railway Co. (b)
$
96,447,967
 
394,265
   
CSX Corp.
 
30,989,229
 
2,824,709
   
Norfolk Southern Corp.
 
195,667,592
         
$
323,104,788
       
Total Transportation
$
323,104,788
       
Automobiles & Components - 4.3 %
   
       
Auto Parts & Equipment - 3.0 %
   
 
689,963
   
BorgWarner, Inc. *
$
54,983,151
 
3,802,683
   
Johnson Controls, Inc.
 
158,077,532
         
$
213,060,683
       
Automobile Manufacturers - 1.3 %
   
 
5,008,640
   
Ford Motor Corp. * (b)
$
74,678,822
 
662,897
   
General Motors Co. * (b)
 
20,569,694
         
$
95,248,516
       
Total Automobiles & Components
$
308,309,199
       
Consumer Durables & Apparel - 1.0 %
   
       
Apparel, Accessories & Luxury Goods - 1.0 %
   
 
1,379,926
   
Coach, Inc. (b)
$
71,811,349
       
Total Consumer Durables & Apparel
$
71,811,349
       
Media - 3.6 %
   
       
Publishing - 3.6 %
   
 
3,444,296
   
John Wiley & Sons, Inc.
$
175,108,009
 
2,092,262
   
McGraw-Hill Co., Inc. (b)
 
82,435,123
         
$
257,543,132
       
Total Media
$
257,543,132
       
Retailing - 3.8 %
   
       
Department Stores - 1.1 %
   
 
394,265
   
Kohl's Corp.
$
20,911,816
 
1,237,787
   
Nordstrom, Inc. (b)
 
55,551,881
         
$
76,463,697
       
General Merchandise Stores - 1.6 %
   
 
2,251,941
   
Target Corp.
$
112,619,569
       
Home Improvement Retail - 0.8 %
   
 
2,282,004
   
Lowe's Companies, Inc.
$
60,313,366
       
Specialty Stores - 0.3 %
   
 
1,088,171
   
Staples, Inc.
$
21,132,281
       
Total Retailing
$
270,528,913
       
Food & Drug Retailing - 3.4 %
   
       
Drug Retail - 2.2 %
   
 
1,196,396
   
CVS/Caremark Corp.
$
41,060,311
 
2,813,571
   
Walgreen Co.
 
112,936,740
         
$
153,997,051
       
Food Distributors - 0.7 %
   
 
1,707,560
   
Sysco Corp. (b)
$
47,299,412
       
Hypermarkets & Supercenters - 0.5 %
   
 
740,232
   
Wal-Mart Stores, Inc.
$
38,529,076
       
Total Food & Drug Retailing
$
239,825,539
       
Food, Beverage & Tobacco - 5.0 %
   
       
Packaged Foods & Meats - 4.4 %
   
 
1,797,058
   
General Mills, Inc.
$
65,682,470
 
1,485,146
   
H.J. Heinz Co., Inc.
 
72,504,828
 
1,897,399
   
Hershey Foods Corp. (b)
 
103,123,636
 
666,800
   
Kellogg Co.
 
35,993,864
 
1,162,588
   
Kraft Foods, Inc.
 
36,458,760
         
$
313,763,558
       
Soft Drinks - 0.6 %
   
 
643,923
   
PepsiCo, Inc.
$
41,475,080
       
Total Food, Beverage & Tobacco
$
355,238,638
       
Household & Personal Products - 2.6 %
   
       
Household Products - 1.8 %
   
 
298,951
   
Clorox Co. (b)
$
20,947,497
 
1,317,337
   
Colgate-Palmolive Co.
 
106,388,136
         
$
127,335,633
       
Personal Products - 0.8 %
   
 
572,965
   
Estee Lauder Co.
$
55,210,907
       
Total Household & Personal Products
$
182,546,540
       
Health Care Equipment & Services - 7.4 %
   
       
Health Care Distributors - 0.3 %
   
 
519,744
   
Cardinal Health, Inc.
$
21,377,071
       
Health Care Equipment - 6.8 %
   
 
888,081
   
Baxter International, Inc.
$
47,752,115
 
1,518,215
   
Becton, Dickinson & Co.
 
120,880,278
 
938,941
   
C. R. Bard, Inc. (b)
 
93,246,231
 
640,680
   
Covidien, Ltd.
 
33,276,919
 
781,728
   
Medtronic, Inc.
 
30,760,997
 
3,301,967
   
Smith & Nephew Plc
 
37,399,856
 
1,490,419
   
St. Jude Medical, Inc.
 
76,398,878
 
739,246
   
Stryker Corp. (b)
 
44,946,157
         
$
484,661,431
       
Health Care Services - 0.3 %
   
 
361,692
   
Medco Health Solutions, Inc. *
$
20,312,623
       
Total Health Care Equipment & Services
$
526,351,125
       
Pharmaceuticals & Biotechnology - 4.5 %
   
       
Biotechnology - 0.4 %
   
 
538,070
   
Amgen, Inc. *
$
28,759,842
       
Pharmaceuticals - 4.1 %
   
 
1,577,749
   
Abbott Laboratories, Inc.
$
77,388,588
 
825,824
   
Eli Lilly & Co.
 
29,044,230
 
596,227
   
Johnson & Johnson Co.
 
35,326,450
 
727,027
   
Merck & Co., Inc.
 
23,999,161
 
2,759,853
   
Pfizer, Inc.
 
56,052,614
 
1,359,307
   
Teva Pharmaceutical Industries, Ltd.
 
68,196,432
         
$
290,007,475
       
Total Pharmaceuticals & Biotechnology
$
318,767,317
       
Banks - 2.7 %
   
       
Diversified Banks - 1.8 %
   
 
926,522
   
Comerica, Inc. (b)
$
34,021,888
 
1,952,202
   
U.S. Bancorp
 
51,596,699
 
1,328,869
   
Wells Fargo  & Co.
 
42,125,147
         
$
127,743,734
       
Regional Banks - 0.9 %
   
 
2,956,985
   
KeyCorp
$
26,258,027
 
640,680
   
PNC Bank Corp.
 
40,356,433
         
$
66,614,460
       
Total Banks
$
194,358,194
       
Diversified Financials - 8.3 %
   
       
Asset Management & Custody Banks - 5.4 %
   
 
709,676
   
Franklin Resources, Inc.
$
88,766,274
 
1,094,084
   
Northern Trust Corp.
 
55,524,763
 
1,577,059
   
State Street Corp.
 
70,873,031
 
1,492,975
   
T. Rowe Price Associates, Inc. (b)
 
99,163,400
 
2,121,243
   
The Bank of New York Mellon Corp.
 
63,361,528
         
$
377,688,996
       
Consumer Finance - 0.4 %
   
 
649,157
   
American Express Co.
$
29,341,896
       
Diversified Financial Services - 1.5 %
   
 
3,549,565
   
Bank of America Corp.
$
47,315,701
 
1,264,604
   
J.P. Morgan Chase & Co.
 
58,298,244
         
$
105,613,945
       
Investment Banking & Brokerage - 0.6 %
   
 
1,601,291
   
Morgan Stanley Co.
$
43,747,270
       
Specialized Finance - 0.4 %
   
 
98,566
   
CME Group, Inc.
$
29,722,577
       
Total Diversified Financials
$
586,114,684
       
Insurance - 2.5 %
   
       
Property & Casualty Insurance - 2.5 %
   
 
2,314,728
   
Chubb Corp. (b)
$
141,915,974
 
591,397
   
The Travelers Companies, Inc.
 
35,176,294
         
$
177,092,268
       
Total Insurance
$
177,092,268
       
Software & Services - 3.6 %
   
       
Application Software - 0.6 %
   
 
1,222,615
   
Adobe Systems, Inc. *
$
40,541,913
       
Data Processing & Outsourced Services - 1.7 %
   
 
1,142,579
   
Automatic Data Processing, Inc.
$
58,625,728
 
544,874
   
DST Systems, Inc.
 
28,780,245
 
543,346
   
Fiserv, Inc. * (b)
 
34,078,661
         
$
121,484,634
       
IT Consulting & Other Services - 0.7 %
   
 
297,177
   
IBM Corp.
$
48,460,653
       
Systems Software - 0.6 %
   
 
1,182,794
   
Microsoft Corp.
$
29,995,656
 
443,548
   
Oracle Corp.
 
14,801,197
         
$
44,796,853
       
Total Software & Services
$
255,284,053
       
Technology Hardware & Equipment - 4.7 %
   
       
Communications Equipment - 2.0 %
   
 
1,823,474
   
Cisco Systems, Inc.
$
31,272,579
 
308,019
   
Motorola Mobility Holdings, Inc. * (b)
 
7,515,664
 
352,021
   
Motorola Solutions, Inc. *
 
15,731,818
 
3,921,554
   
Nokia Corp. (A.D.R.) (b)
 
33,372,425
 
492,831
   
Qualcomm, Inc.
 
27,021,924
 
492,831
   
Research In Motion, Inc. * (b)
 
27,879,450
         
$
142,793,860
       
Computer Hardware - 1.6 %
   
 
2,688,107
   
Hewlett-Packard Co.
$
110,131,744
       
Office Electronics - 1.1 %
   
 
1,839,097
   
Canon, Inc. (A.D.R.) (b)
$
79,724,855
       
Total Technology Hardware & Equipment
$
332,650,459
       
Semiconductors - 4.6 %
   
       
Semiconductor Equipment - 1.3 %
   
 
2,953,535
   
Applied Materials, Inc.
$
46,134,217
 
931,450
   
ASM Lithography Holdings NV (b)
 
41,449,525
         
$
87,583,742
       
Semiconductors - 3.3 %
   
 
739,246
   
Altera Corp. (b)
$
32,541,609
 
1,675,625
   
Analog Devices, Inc.
 
65,986,113
 
2,836,242
   
Intel Corp.
 
57,207,001
 
2,319,755
   
Texas Instruments, Inc.
 
80,170,733
         
$
235,905,456
       
Total Semiconductors
$
323,489,198
       
Telecommunication Services - 1.6 %
   
       
Integrated Telecommunication Services - 1.6 %
   
 
2,267,022
   
AT&T Corp.
$
69,370,873
 
242,822
   
Frontier Communications Corp. (b)
 
1,995,997
 
1,011,591
   
Verizon Communications, Inc.
 
38,986,717
         
$
110,353,587
       
Total Telecommunication Services
$
110,353,587
       
Utilities - 1.2 %
   
       
Electric Utilities - 0.8 %
   
 
586,469
   
PPL Corp.
$
14,837,666
 
1,075,751
   
Southern Co.
 
40,996,871
         
$
55,834,537
       
Multi-Utilities - 0.4 %
   
 
931,549
   
Public Service Enterprise Group, Inc.
$
29,353,109
       
Total Utilities
$
85,187,646
       
TOTAL COMMON STOCKS
   
       
(Cost  $4,100,031,684)
$
7,079,990,991
 
Principal
         
 
Amount ($)
   
TEMPORARY CASH INVESTMENTS -4.7 %
   
       
Securities Lending Collateral  - 4.7 % (c)
   
       
Certificates of Deposit:
   
 
9,546,356
   
Bank of Nova Scotia, 0.31%, 9/29/11
$
9,546,356
 
6,682,449
   
BBVA Group NY, 1.05%, 7/26/11
 
6,682,449
 
9,546,356
   
BNP Paribas Bank NY, 0.34%, 5/9/11
 
9,546,356
 
9,546,356
   
Canadian Imperial Bank of Commerce NY, 0.23%, 4/27/11
 
9,546,356
 
9,546,356
   
DnB NOR Bank ASA NY, 0.24%, 6/7/11
 
9,546,356
 
4,772,972
   
National Australia Bank NY, 0.32%, 10/19/11
 
4,772,972
 
9,546,356
   
Nordea NY, 0.3%, 4/13/11
 
9,546,356
 
9,546,356
   
RoboBank Netherland NV NY, 0.33%, 8/8/11
 
9,546,356
 
9,546,356
   
Royal Bank of Canada NY, 0.38%, 12/2/11
 
9,546,356
 
9,546,356
   
Skandinav Enskilda Bank NY, 0.38%, 6/7/11
 
9,546,356
 
4,773,178
   
SOCGEN NY, 0.25%, 4/11/11
 
4,773,178
 
3,818,542
   
SOCGEN NY, 0.37%, 6/10/11
 
3,818,542
 
9,546,356
   
Svenska NY, 0.28%, 5/12/11
 
9,546,356
 
9,546,356
   
Westpac Banking Corp. NY, 0.38%, 12/6/11
 
9,546,356
         
$
115,510,701
       
Commercial Paper:
   
 
3,818,542
   
American Honda Finance, 0.35%, 1/11/12
$
3,818,542
 
3,825,124
   
American Honda Finance, 1.06%, 6/20/11
 
3,825,124
 
3,501,411
   
Australia & New Zealand Banking Group, 0.91%, 8/4/11
 
3,501,411
 
3,816,325
   
BBVLON, 0.55%, 5/9/11
 
3,816,325
 
5,726,445
   
BBVLON, 0.43%, 4/21/11
 
5,726,445
 
9,540,787
   
BCSFUN, 0.25%, 6/24/11
 
9,540,787
 
8,588,555
   
CBAPP, 0.26%, 5/23/11
 
8,588,555
 
9,706,492
   
Caterpillar Financial Services Corp., 1.06%, 6/24/11
 
9,706,492
 
9,546,679
   
Federal Home Loan Bank, 0.31%, 6/1/11
 
9,546,679
 
954,476
   
General Electric Capital Corp., 0.39%, 6/6/11
 
954,476
 
4,773,556
   
General Electric Capital Corp., 0.39%, 4/28/11
 
4,773,556
 
7,634,963
   
HSBC, 0.25%, 5/11/11
 
7,634,963
 
4,585,964
   
JPMorgan Chase & Co., 0.43%, 12/21/11
 
4,585,964
 
3,346,447
   
JPMorgan Chase & Co., 1.06%, 6/13/11
 
3,346,447
 
4,771,196
   
NABPP, 0.25%, 6/1/11
 
4,771,196
 
7,630,898
   
NORDNA, 0.27%, 7/18/11
 
7,630,898
 
7,636,597
   
PARFIN, 0.23%, 4/11/11
 
7,636,597
 
4,767,678
   
SANCPU, 0.68%, 6/1/11
 
4,767,678
 
5,727,393
   
SANCPU, 0.44%, 4/7/11
 
5,727,393
 
5,718,870
   
SANCPU, 0.73%, 6/17/11
 
5,718,870
 
4,772,549
   
SOCNAM, 0.37%, 4/14/11
 
4,772,549
 
4,771,608
   
SOCNAM, 0.37%, 5/3/11
 
4,771,608
 
9,546,356
   
Toyota Motor Credit Corp., 0.38%, 9/8/11
 
9,546,356
 
5,726,997
   
VARFUN, 0.27%, 4/20/11
 
5,726,997
 
2,866,936
   
Wachovia, 0.46%, 3/1/12
 
2,866,936
 
3,820,244
   
Wachovia, 0.43%, 10/15/11
 
3,820,244
 
1,910,782
   
Wells Fargo & Co., 0.39%, 1/24/12
 
1,910,782
         
$
149,033,870
       
Tri-party Repurchase Agreements:
   
 
4,894,798
   
Barclays Capital Plc, 0.12%, 4/1/11
$
4,894,798
 
19,092,711
   
HSBC Bank USA NA, 0.13%, 4/1/11
 
19,092,711
 
14,319,533
   
RBS Securities, Inc., 0.12%, 4/1/11
 
14,319,533
         
$
38,307,042
 
Shares
   
Money Market Mutual Funds:
   
 
15,274,168
   
Dreyfus Preferred Money Market Fund
$
15,274,168
 
15,274,169
   
Fidelity Prime Money Market Fund
 
15,274,169
         
$
30,548,337
       
Total Securities Lending Collateral
$
333,399,950
       
TOTAL TEMPORARY CASH INVESTMENTS
   
       
(Cost  $333,399,950)
$
333,399,950
             
       
TOTAL INVESTMENT IN SECURITIES - 104.5%
   
       
(Cost  $4,433,431,634) (a)
$
7,413,390,941
             
       
OTHER ASSETS AND LIABILITIES - (4.5)%
$
(316,445,440)
             
       
TOTAL NET ASSETS - 100.0%
$
7,096,945,501
             
 
*
   
Non-Income producing security.
   
             
 
(a)
   
At March 31, 2011, the net unrealized loss on investments based on
   
       
cost for federal Income tax purposes of $4,433,431,634 was as follows:
   
             
       
Aggregate gross unrealized gain for all investments in which
   
       
there is an excess of value over tax cost
$
3,116,403,386
             
       
Aggregate gross unrealized loss for all investments in which
   
       
there is an excess of tax cost over value
 
(136,444,079)
             
       
Net unrealized gain
$
2,979,959,307
             
 
(b)
   
At March 31, 2011, the following securities were out on loan:
   
             
 
Shares
   
Description
 
Value
 
           41,600
   
Airgas, Inc.
$
            2,818,400
 
         296,900
   
Alcoa, Inc.
 
            5,344,200
 
           21,400
   
Altera Corp.
 
               957,650
 
         836,100
   
ASM Lithography Holdings NV
 
          37,835,925
 
         828,800
   
C. R. Bard, Inc.
 
          83,501,600
 
         158,700
   
Canadian National Railway Co.
 
          12,061,200
 
         370,600
   
Canon, Inc. (A.D.R.)
 
          16,897,600
 
           94,800
   
Chubb Corp.
 
            5,901,300
 
         274,000
   
Clorox Co.
 
          19,591,000
 
           22,100
   
Coach, Inc.
 
            1,182,350
 
         150,900
   
Comerica, Inc.
 
            5,658,750
 
         570,300
   
Ensco Plc
 
          34,069,525
 
                300
   
Fiserv, Inc. *
 
                 19,200
 
           56,800
   
Ford Motor Corp. *
 
               866,200
 
             5,900
   
Frontier Communications Corp.
 
                 48,675
 
           11,100
   
General Motors Co. *
 
               357,975
 
           14,100
   
Helmerich & Payne, Inc.
 
               972,900
 
         403,700
   
Hershey Foods Corp.
 
          22,607,200
 
           12,100
   
McGraw-Hill Co., Inc.
 
               496,100
 
           33,500
   
Motorola Mobility Holdings, Inc. *
 
               845,875
 
      3,938,800
   
Nokia Corp. (A.D.R.)
 
          35,449,200
 
           34,800
   
Nordstrom, Inc.
 
            1,600,800
 
         201,700
   
Research In Motion, Inc. *
 
          11,749,025
 
           12,100
   
Rockwell International Corp.
 
            1,161,600
 
         129,900
   
Stryker Corp.
 
            8,053,800
 
         288,200
   
Sysco Corp.
 
            8,213,700
 
         155,000
   
T. Rowe Price Associates, Inc.
 
          10,501,250
 
           56,200
   
United Technologies Corp.
 
            4,833,200
       
Total
$
        333,596,200
             
 
(c)
   
Securities lending collateral is managed by Credit Suisse AG, New York Branch.
   
             
             
Various inputs are used in determining the value of the Fund’s investments.  These inputs are summarized in the three broad levels listed below.
Highest priority is given to Level 1 inputs and lowest priority is given to Level 3.
   
Level 1 – quoted prices in active markets for identical securities
   
Level 2 – other significant observable inputs (Including quoted prices for similar securities, interest rates, prepayment speeds, credit risk, etc.)
Level 3 – significant unobservable inputs (Including the Fund’s own assumptions in determining fair value of investments)
             
The following is a summary of the inputs used as of March 31, 2011, in valuing the Fund’s assets:
   
             




   
Level 1
   
Level 2
   
Level 3
   
Total
 
Common Stocks
  $ 7,079,990,991     $ -     $ -     $ 7,079,990,991  
Temporary Cash Investments
    -       302,851,613       -       302,851,613  
Money Market Mutual Funds
    30,548,337       -       -       30,548,337  
Total
  $ 7,110,539,328     $ 302,851,613     $ -     $ 7,413,390,941  


ITEM 2. CONTROLS AND PROCEDURES.

(a) Disclose the conclusions of the registrant's principal executive
and principal financial officers, or persons performing similar functions,
regarding the effectiveness of the registrant's disclosure
controls and procedures (as defined in Rule 30a-3(c) under the Act (17 CFR
270.30a-3(c))) as of a date within 90 days of the filing date of the report
that includes the disclosure required by this paragraph, based on the
evaluation of these controls and procedures required by Rule 30a-3(b)
under the Act (17 CFR 270.30a-3(b))) and Rule 13a-15(b) or 15d-15(b)
under the Exchange Act (17 CFR 240.13a-15(b) or 240.15d-15(b)).

The registrant's principal executive officer and principal financial officer
have concluded that the registrant's disclosure controls and procedures are
effective based on their evaluation of these controls and procedures as of
a date within 90 days of the filing date of this report.

(b) Disclose any change in the registrant's internal controls over financial
reporting (as defined in Rule 30a-3(d) under the Act (17 CFR 270.30a-3(d))
that occurred during the registrant's last fiscal quarter that has materially
affected, or is reasonably likely to materially affect, the registrant's
internal control over financial reporting.

There were no significant changes in the registrant's internal control over
financial reporting that occurred during the second fiscal quarter of the
period covered by this report that have materially affected, or are
reasonably likely to materially affect, the registrant's internal control
over financial reporting.



ITEM 3. EXHIBITS.

(a) A separate certification for each principal executive officer and principal
financial officer of the registrant as required by Rule 30a-2(a) under the Act
(17 CFR 270.30a-2(a)).

Filed herewith.



<PAGE>


                                   SIGNATURES

                          [See General Instruction F]


Pursuant to the requirements of the Securities Exchange Act of 1934 and the
Investment Company Act of 1940, the registrant has duly caused this report to be
signed on its behalf by the undersigned, thereunto duly authorized.


(Registrant) Pioneer Fund

By (Signature and Title)* /s/ John F. Cogan, Jr.
John F. Cogan, Jr, President

Date May 27, 2011


Pursuant to the requirements of the Securities Exchange Act of 1934 and the
Investment Company Act of 1940, this report has been signed below by the
following persons on behalf of the registrant and in the capacities and on the
dates indicated.


By (Signature and Title)* /s/ John F. Cogan, Jr.
John F. Cogan, Jr., President

Date May 27, 2011



By (Signature and Title)* /s/ Mark Bradley
Mark Bradley, Treasurer

Date May 27, 2011

* Print the name and title of each signing officer under his or her signature.
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