American Century Mutual Funds, Inc.

STATEMENT OF ADDITIONAL INFORMATION SUPPLEMENT

BALANCED FUND * CAPITAL GROWTH FUND * CAPITAL VALUE FUND
FOCUSED GROWTH FUND * FUNDAMENTAL EQUITY FUND * GIFTRUST® FUND * GROWTH FUND
HERITAGE FUND * AMERICAN CENTURY-MASON STREET MID CAP GROWTH FUND
NEW OPPORTUNITIES FUND * NEW OPPORTUNITIES II FUND * NT GROWTH FUND
NT VISTA(SM) FUND * SELECT FUND * AMERICAN CENTURY-MASON STREET SMALL CAP GROWTH FUND
ULTRA® FUND * VEEDOT® FUND * VISTA(SM) FUND

[american century investments logo and text logo]

Supplement dated December 3, 2007 * Statement of Additional Information dated September
28, 2007

On December 3, 2007, Balanced Advisor Class shareholders will receive Investor
Class shares of Balanced in exchange for their Advisor Class shares.
Accordingly, the Advisor Class shares of Balanced will no longer be offered.

On December 3, 2007, Growth C Class shareholders will receive Advisor Class
shares of Growth in exchange for their C Class shares. Accordingly, the C Class
shares of Growth will no longer be offered.

On December 3, 2007, Vista C Class shareholders will receive Advisor Class
shares of Vista in exchange for their C Class shares. Accordingly, the C Class
shares of Vista will no longer be offered.

THE FOLLOWING REPLACES THE BALANCED, GROWTH AND VISTA SECTIONS OF THE TABLE ON
PAGES 2-4:

FUND                                TICKER SYMBOL               INCEPTION DATE
--------------------------------------------------------------------------------
Balanced
  Investor Class                    TWBIX                       10/20/1988
--------------------------------------------------------------------------------
  Institutional Class               ABINX                       05/01/2000
--------------------------------------------------------------------------------
Growth
  Investor Class                    TWCGX                       10/31/1958
--------------------------------------------------------------------------------
  Institutional Class               TWGIX                       06/16/1997
--------------------------------------------------------------------------------
  R Class                           AGWRX                       08/29/2003
--------------------------------------------------------------------------------
  Advisor Class                     TCRAX                       06/04/1997
--------------------------------------------------------------------------------
Vista
  Investor Class                    TWCVX                       11/25/1983
--------------------------------------------------------------------------------
  Institutional Class               TWVIX                       11/14/1996
--------------------------------------------------------------------------------
  R Class                           AVTRX                       07/29/2005
--------------------------------------------------------------------------------
  Advisor Class                     TWVAX                       10/02/1996
--------------------------------------------------------------------------------




THE FOLLOWING REPLACES THE BALANCED, CAPITAL VALUE, GROWTH AND VISTA SECTIONS OF
THE TABLE ON PAGES 54-57:

FUND                     CLASS                     PERCENTAGE OF STRATEGY ASSETS
--------------------------------------------------------------------------------
Balanced                 Investor                  0.900% of first $1 billion
                                                   0.800% over $1 billion
                         -------------------------------------------------------
                         Institutional             0.700% of first $1 billion
                                                   0.600% over $1 billion
--------------------------------------------------------------------------------
Capital Value            Investor and              1.10% of first $500 million
                         Advisor                   1.00% of next $500 million
                                                   0.90% over $1 billion
                         -------------------------------------------------------
                         Institutional             0.90% of first $500 million
                                                   0.80% of next $500 million
                                                   0.70% over $1 billion
--------------------------------------------------------------------------------
Growth                   Investor, R               1.000% of first $2.5 billion
                         and Advisor               0.995% of next $2.5 billion
                                                   0.980% of next $2.5 billion
                                                   0.970% of next $2.5 billion
                                                   0.960% of next $2.5 billion
                                                   0.950% of next $2.5 billion
                                                   0.940% of next $2.5 billion
                                                   0.930% of next $2.5 billion
                                                   0.920% of next $2.5 billion
                                                   0.910% of next $2.5 billion
                                                   0.900% of next $5 billion
                                                   0.800% over $30 billion
                         -------------------------------------------------------
                         Institutional             0.800% of first $2.5 billion
                                                   0.795% of next $2.5 billion
                                                   0.780% of next $2.5 billion
                                                   0.770% of next $2.5 billion
                                                   0.760% of next $2.5 billion
                                                   0.750% of next $2.5 billion
                                                   0.740% of next $2.5 billion
                                                   0.730% of next $2.5 billion
                                                   0.720% of next $2.5 billion
                                                   0.710% of next $2.5 billion
                                                   0.700% of next $5 billion
                                                   0.600% over $30 billion
--------------------------------------------------------------------------------
Vista                    Investor, R               1.000%
                         and Advisor
                         -------------------------------------------------------
                         Institutional             0.800%
--------------------------------------------------------------------------------

THE FOLLOWING REPLACES THE SECOND PARAGRAPH UNDER MULTIPLE CLASS STRUCTURE ON
PAGE 76:

The Investor Class is made available to investors directly from American Century
and/or through some financial intermediaries. Investor Class shares charge a
single unified management fee, without any load or commission payable to
American Century. Additional information regarding eligibility for Investor
Class shares may be found in the funds' prospectuses. The Institutional Class is
made available to institutional shareholders or through financial intermediaries
whose clients do not require the same level of shareholder and administrative
services from the advisor as Investor Class shareholders. As a result, the
advisor is able to charge these classes a lower total management fee. The A, B,
C and Advisor Classes also are made available through financial intermediaries,
for purchase by individual investors who receive advisory and personal services
from the intermediary. The R Class is made available through financial
intermediaries and is generally used in 401(k) and other retirement plans. The
unified management fee for the A, B, C, R and Advisor Classes is the same as for
Investor Class, but the A, B, C, R and Advisor Class shares each are subject to
a separate Master Distribution and Individual Shareholder Services Plan (the A
Class Plan, B Class Plan, C Class Plan, R Class Plan and Advisor Class Plan,
respectively, and collectively, the plans) described below. The plans have been
adopted by the funds' Board of Directors in accordance with Rule 12b-1 adopted
by the SEC under the Investment Company Act.


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THE FOLLOWING REPLACES THE ADVISOR CLASS PLAN AND ADVISOR CLASS PLAN (BALANCED
AND VISTA) SECTIONS ON PAGES 84-88:

ADVISOR CLASS PLAN(1)

As described in the prospectuses, the funds' Advisor Class shares are made
available to participants in employer-sponsored retirement plans and to persons
purchasing through broker-dealers, banks, insurance companies, and other
financial intermediaries that provide various administrative, shareholder and
distribution services. The funds' distributor enters into contracts with various
banks, broker-dealers, insurance companies and other financial intermediaries,
with respect to the sale of the funds' shares and/or the use of the funds'
shares in various investment products or in connection with various financial
services.

Certain recordkeeping and administrative services that are provided by the
funds' transfer agent for the Investor Class shareholders may be performed by a
plan sponsor (or its agents) or by a financial intermediary for Advisor Class
investors. In addition to such services, the financial intermediaries provide
various distribution services.

To make the funds' shares available through such plans and financial
intermediaries, and to compensate them for these services, the funds' Board of
Directors has adopted the Advisor Class Plan. Prior to September 4, 2007 for
Balanced, Heritage, Select, Ultra and Vista, and December 3, 2007 for Capital
Value and Growth, the Advisor Class Plan required the Advisor Class to pay 0.50%
annually of the aggregate average daily net assets of the funds' Advisor Class
shares, 0.25% for certain ongoing shareholder and administrative services (as
described below) and 0.25% for distribution services, including past
distribution services (as described below). However, at shareholder meetings on
July 27, 2007 and September 25, 2007, the Advisor Class shareholders approved a
decrease in the fee required by the Advisor Class Plan of 0.25%, and a
corresponding increase in the Advisor Class management fee. This change was made
because the administrative services portion of the 12b-1 fee does not need to be
made out of the 12b-1 plan, but may properly be made out of the funds' unified
fee, consistent with the other classes of the funds. This change resulted in no
difference in the overall fee for the Advisor Class, but will lower the amount
of the 12b-1 fee charged under the Advisor Class Plan from and after September
4, 2007 for Balanced and Vista, and December 3, 2007 for Capital Value and
Growth. After those dates, pursuant to the Advisor Class Plan, the Advisor Class
pays the funds' distributor 0.25% annually of the aggregate average daily net
assets of the funds' Advisor Class shares, which is paid for certain ongoing
individual shareholder services (as described below) and for distribution
services, including past distribution services (as described below). This
payment is fixed at 0.25% and is not based on expenses incurred by the
distributor. During the fiscal year ended October 31, 2006, the aggregate amount
of fees paid under the Advisor Class Plan was:

Balanced                  $78,178
Capital Value             $77,994
Growth                   $412,928
Heritage                 $203,164
Select                   $130,626
Ultra                  $2,678,076
Vista                  $1,097,050

The distributor then makes these payments to the financial intermediaries
(including underwriters and broker-dealers, who may use some of the proceeds to
compensate sales personnel) who offer the Advisor Class shares in payment for
provision of the services, as described below. No portion of these payments is
used by the distributor to pay for advertising, printing costs or interest
expenses.

(1)  AS OF SEPTEMBER 4, 2007, THE ADVISOR CLASSES OF HERITAGE, SELECT AND
     ULTRA WERE EITHER RENAMED A CLASS OR COMBINED WITH AN EXISTING A CLASS AND
     BECAME SUBJECT TO THE A CLASS PLAN.


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Prior to September 4, 2007 for Balanced, Heritage, Select, Ultra and Vista, and
December 3, 2007 for Capital Value and Growth, 0.25% of the fee charged to the
Advisor Class Plan was for a variety of shareholder services, including, but not
limited to:

(a)  receiving, aggregating and processing purchase, exchange and
     redemption requests from beneficial owners (including contract owners of
     insurance products that utilize the funds as underlying investment media)
     of shares and placing purchase, exchange and redemption orders with the
     funds' distributor;

(b)  providing shareholders with a service that invests the assets of their
     accounts in shares pursuant to specific or pre-authorized instructions;

(c)  processing dividend payments from a fund on behalf of shareholders and
     assisting shareholders in changing dividend options, account designations
     and addresses;

(d)  providing and maintaining elective services such as check writing and
     wire transfer services;

(e)  acting as shareholder of record and nominee for beneficial owners;

(f)  maintaining account records for shareholders and/or other beneficial
     owners;

(g)  issuing confirmations of transactions;

(h)  providing subaccounting with respect to shares beneficially owned by
     customers of third parties or providing the information to a fund as
     necessary for such subaccounting;

(i)  preparing and forwarding investor communications from the funds (such
     as proxies, shareholder reports, annual and semi-annual financial
     statements and dividend, distribution and tax notices) to shareholders
     and/or other beneficial owners; and

(j)  providing other similar administrative and sub-transfer agency
     services.

Shareholder services do not include those activities and expenses that are
primarily intended to result in the sale of additional shares of the funds.
During the fiscal year ended October 31, 2006, the amount of fees paid under the
Advisor Class Plan for shareholder services was:

Balanced                   $39,089
Capital Value              $38,997
Growth                    $206,464
Heritage                  $101,582
Select                     $65,313
Ultra                   $1,339,038
Vista                     $548,525

Although these services are still being provided by the financial
intermediaries, after September 4, 2007 for Balanced and Vista, and December 3,
2007 for Capital Value and Growth, they will be reimbursed by the funds' advisor
out of the unified management fee rather than out of a 12b-1 fee, as described
above.

Distribution services include any activity undertaken or expense incurred that
is primarily intended to result in the sale of Advisor Class shares, which
services may include but are not limited to:

(a)  paying sales commissions, on-going commissions and other payments to
     brokers, dealers, financial institutions or others who sell Advisor Class
     shares pursuant to selling agreements;

(b)  compensating registered representatives or other employees of the
     distributor who engage in or support distribution of the funds' Advisor
     Class shares;

(c)  paying and compensating expenses (including overhead and telephone
     expenses) of the distributor;

(d)  printing prospectuses, statements of additional information and
     reports for other-than-existing shareholders;

(e)  preparing, printing and distributing of sales literature and
     advertising materials provided to the funds' shareholders and prospective
     shareholders;

(f)  receiving and answering correspondence from prospective shareholders,
     including distributing prospectuses, statements of additional information,
     and shareholder reports;

(g)  providing facilities to answer questions from prospective shareholders
     about fund shares;

(h)  complying with federal and state securities laws pertaining to the
     sale of fund shares;

(i)  assisting shareholders in completing application forms and selecting
     dividend and other account options;

(j)  providing other reasonable assistance in connection with the
     distribution of fund shares;


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(k)  organizing and conducting of sales seminars and payments in the form
     of transactional and compensation or promotional incentives;

(l)  profit on the foregoing;

(m)  paying service fees for the provision of personal, continuing services
     to investors, as contemplated by the Conduct Rules of the FINRA; and

(n)  such other distribution and services activities as the advisor
     determines may be paid for by the funds pursuant to the terms of the
     agreement between the corporation and the funds' distributor and in
     accordance with Rule 12b-1 of the Investment Company Act.

During the fiscal year ended October 31, 2006, the amount of fees paid under the
Advisor Class Plan for distribution services was:

Balanced                 $39,089
Capital Value            $38,997
Growth                  $206,464
Heritage                $101,582
Select                   $65,313
Ultra                 $1,339,038
Vista                   $548,525

Beginning on September 4, 2007 for Balanced and Vista, and December 3, 2007 for
Capital Value and Growth, a portion of the 12b-1 fee will be paid to the
distributor for certain individual shareholder services. These payments may be
made for a variety of individual shareholder services, including, but not
limited to:

(a)  providing individualized and customized investment advisory services,
     including the consideration of shareholder profiles and specific goals;

(b)  creating investment models and asset allocation models for use by
     shareholders in selecting appropriate funds;

(c)  conducting proprietary research about investment choices and the
     market in general;

(d)  periodic rebalancing of shareholder accounts to ensure compliance with
     the selected asset allocation;

(e)  consolidating shareholder accounts in one place; and

(f)  other individual services.

Individual shareholder services do not include those activities and expenses
that are primarily intended to result in the sale of additional shares of the
funds.


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American Century Investment Services, Inc., Distributor

©2007 American Century Proprietary Holdings, Inc. All rights reserved.

The American Century Investments logo, American Century and American Century
Investments are service marks of American Century Proprietary Holdings, Inc.

SH-SPL-57457 0712