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

                                   FORM 24F-2
                        Annual Notice of Securities Sold
                             Pursuant to Rule 24f-2


1.   Name and address of issuer:

     Pioneer Fund
     60 State Street
     Boston, MA 02109-1820

2.   Name of each series or class of securities for which this Form is filed (if
     the Form is being  filed for all series and  classes of  securities  of the
     issuer, check the box but do not list series or classes): X

3.   Investment Company Act File Number:  811-07613
     Securities Act File Number: 2-25980

4(a).Last day of fiscal year for which this notice is filed: December 31, 2005

4(b).__ Check  box if this  notice  is being  filed  late  (i.e.,  more  than 90
     calendar days after the end of the issuer's fiscal year).  (See Instruction
     A.2)



Note:  If the Form is being filed late,  interest must be paid on the
       registration fee due

4(c).__ Check box if this is the last time the issuer will be filing this form.

5.   Calculation of registration fee:

     (i)   Aggregate sale price of securities sold
           during the fiscal year pursuant to
           Section 24(f):                                      $903,107,068.93

     (ii)  Aggregate price of securities redeemed or repurchased during
           the fiscal year:                     $1,228,434,121.00

     (iii) Aggregate  price of  securities  redeemed or  repurchased  during any
           prior  fiscal year ending no earlier  than October 11, 1995 that were
           not previously used to reduce registration fees payable to the
           Commission:                         $329,307,949.34

     (iv) Total available redemption credits [add
           Items 5(ii)and 5(iii):                              $1,557,742,070.34


     (v)   Net sales-if Item 5(i) is greater than Item 5(iv)[subtract Item 5(iv)
           from Item 5(i)]:                                      $0

     (vi)  Redemption  credits  available for use in future years---if Item 5(i)
           is  less  than  Item  5(iv)[subtract  Item  5(iv)  from  Item  5(i)]:
           $654,635,001.41

     (vii) Multiplier for determining registration fee
           (See instruction C.9):                                  x .00010700

     (viii)Registration fee due [multiply Item 5(v) by
           Item 5(vii)](enter "0" if no fee is due):               = $0

6.   Prepaid Shares

     If the  response  to Item 5(i) was  determined  by  deducting  an amount of
     securities that were  registered  under the Securities Act of 1933 pursuant
     to rule 24e-2 as in effect before October 11, 1997,  then report the amount
     of securities  (number of shares or other units)  deducted  here:  None. If
     there are a number of shares or other units that were  registered  pursuant
     to rule 24e-2 remaining unsold at the end of the fiscal year for which this
     form is filed that are  available  for use by the  issuer in future  fiscal
     years, then state that number here: None.

7.   Interest  due - if this Form is being filed more than 90
     days after the end of the issuer's fiscal year
     (See Instruction D):     N/A

8.   Total of the amount of the registration fee due plus any interest due [line
     5(viii) plus line 7]: $0

9.   Date  the  registration  fee  and  any  interest  payment  was  sent to the
     Commission's lockbox depository:  N/A

          Method of Delivery:

               ______  Wire Transfer

               ______  Mail or other means

                                   SIGNATURES

     This report has been signed below by the following persons on behalf of the
     issuer and in the capacities and on the dates indicated.


     By   /s/Christopher J. Kelley
             Christopher J. Kelley
             Assistant Secretary

     Date:  March 24, 2006