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

                                    Form 13F

                              Form 13F COVER PAGE

Report for the Calendar Year or Quarter Ended: 03/31/2008

Check here if Amendment [  ]; Amendment Number:
This Amendment (Check only one.): [  ] is a restatement.
                                  [  ] adds new holdings entries.

Institutional Investment Manager Filing this Report:

Name:    American Century Investment Management, Inc.
Address: 4500 Main

         Kansas City, MO  64111

13F File Number:  28-01091

The institutional investment manager filing this report and the person by whom
it is signed hereby represent that the person signing the report is authorized
to submit it, that all information contained herein is true, correct and
complete, and that it is understood that all required items, statements,
schedules, lists, and tables, are considered integral parts of this form.

Person Signing this Report on Behalf of Reporting Manager:

Name:      Charles A. Etherington
Title:     Senior Vice President
Phone:     816-531-5575

Signature, Place, and Date of Signing:

     /s/Charles A. Etherington     Kansas City, MO     May 13, 2008


Report Type (Check only one.):

[  ]         13F HOLDINGS REPORT.

[ X]         13F NOTICE.

[  ]         13F COMBINATION REPORT.


List of Other Managers Reporting for this Manager:

       Form 13F File Number          Name

       28-11918                      American Century Companies, Inc.