SECURITIES EXCHANGE COMMISSION


                              Washington, DC 20549

                    Under the Securities Exchange Act of 1934
                               (Amendment No. 3 )

                           MISSISSIPPI CHEMICAL CORP.
                                (Name of Issuer)
                                     Common
                         (Title of Class of Securities)


              Date of Event Which Requires Filing of this Statement
                                December 31, 2000

                 Check the appropriate box to designate the rule
                    pursuant to which this Schedule is filed


                                 X Rule 13d-2(b)
                                    605288208

                                 (CUSIP NUMBER)















1)       Name of Reporting                       Pioneer
         Person                                  Investment
                                                 Management Inc.

         IRS Identification                      13-1961193
         No. of Above

2)       Check the Appropriate Box               (a)
         of A Member of  Group
         (See Instructions)                      (b)  X

3)       SEC Use Only

4)       Citizenship of Place of
         Organization                            Delaware

         Number of                               (5)  Sole Voting       1880000
         Shares                                  Power
         Beneficially Owned                      (6)  Shared Voting     0
         by Each Reporting                       Power
         Person With                             (7)  Sole Dispositive  1880000
                                                 Power
                                                 (8)  Shared Disposi-   0
                                                 tive Power



9)       Aggregate Amount Beneficially           1880000
         Owned by Each
         Reporting Person

10       Check if the aggregate
         Amount in Row  (9) Exclude Certain
         Shares (See
         Instructions)

11       Percent of Class Represented
         By Amount in Row 9.                     7.19%

12)      Type of Reporting
         Person (See Instructions)               IA











Item 1(a)         Name of Issuer.

                  MISSISSIPPI CHEMICAL CORP.

Item 1(b)         Address of Issuer's Principal Executive Offices:


                  Mr. Timothy A. Dawson ,Vice President - Finance
                  MISSISSIPPI CHEMICAL CORP.
                  Highway 49 East
                  Yazoo City, MS 39194

Item 2(a)         Name of Person Filing:

                  Pioneer Investment Management, Inc.

Item 2(b)         Address of Principal Business Office:

                  60 State Street, Boston, MA 02109

Item 2(c)         Citizenship:

                  State of Delaware
                  Pioneer Investment Management, Inc.

Item 2(d)         Title of Class of Securities:

                  Common Stock

Item 2(e)         CUSIP Number:

                  605288208

Item 3)           The person filing this  statement  pursuant to Rule 13d-1(b)
                  or 13d-2(b) is:

                  (d)      Investment Adviser registered under Section
                  203 of the Investment Advisers Act of 1940.







Item 4.  Ownership.

(a)        Amount Beneficially Owned:                                    1880000

(b)        Percent of Class:                                             7.19%


(c)      Number of shares as to which such person has

         (i)      sole power to vote or to direct the vote             1880000

         (ii)     shared power to vote or to direct vote               0

         (iii)    sole power to dispose or to direct disposition of    1880000

         (iv)     shared power to dispose or to direct disposition     0

Item 5.  Ownership of Five Percent or Less of a Class.

         If this statement is being filed to report the fact that as of
         the date  Hereof  the  reporting  person  has ceased to be the
         beneficial  owner of more  than five  percent  of the class of
         securities, check here:


Item 6.  Ownership of More than Five Percent on Behalf of Another Person.

                  Inapplicable.

Item 7.  Identification and Classification of the Subsidiary Which Acquired
         the Security Being Reported On By the Parent Holding Company.

                  Inapplicable.

Item 8.  Identification and Classification of Members of the Group.

                  Inapplicable.

Item 9.  Notice of Dissolution of the Group.

                  Inapplicable.







Item 10. Certification.

By signing below I certify  that,  to the best of my knowledge  and belief,  the
securities  referred to above were  acquired in the ordinary  course of business
and were not  acquired for the purpose of and do not have the effect of changing
or  influencing  the  control  of the  issuer  of such  securities  and were not
acquired in connection with or as a participant in any transactions  having such
purposes or effect.

After reasonable  inquiry and to the best of my knowledge and believe, I certify
that the information set forth in this statement is true, complete and correct.


   January 3, 2001
     Date




     /s/Dorothy B. Bourassa
     Dorothy B. Bourassa
     Secretary