PROSPECTUS AND SAI SUPPLEMENTS

497 1 supp.htm PROSPECTUS AND SAI SUPPLEMENTS PROSPECTUS AND SAI SUPPLEMENTS

American Century Municipal Trust

PROSPECTUS SUPPLEMENT

ARIZONA MUNICIPAL BOND FUND * FLORIDA MUNICIPAL BOND FUND
HIGH-YIELD MUNICIPAL FUND * LONG-TERM TAX-FREE FUND * TAX-FREE BOND FUND
TAX-FREE MONEY MARKET FUND

Supplement dated August 1, 2006 * Prospectuses dated October 1, 2005 and April
1, 2006

ALL REFERENCES TO "QUALIFIED RETIREMENT PLANS" SHOULD BE REPLACED WITH
"EMPLOYER-SPONSORED RETIREMENT PLANS."

B CLASS SHARES ARE NO LONGER AVAILABLE FOR PURCHASE THROUGH EMPLOYER-SPONSORED
RETIREMENT PLANS. HOWEVER, INVESTORS IN SIMPLE IRAS, SEP IRAS AND SARSEP PLANS
ESTABLISHED PRIOR TO AUGUST 1, 2006, MAY MAKE ADDITIONAL PURCHASES.

THE FOLLOWING IS ADDED AS THE FIRST PARAGRAPH UNDER ARIZONA MUNICIPAL
BOND/FLORIDA MUNICIPAL BOND ON PAGE 14 OF THE INVESTOR CLASS PROSPECTUS AND PAGE
15 OF THE A/B/C CLASS PROSPECTUS FOR THE ARIZONA MUNICIPAL BOND AND FLORIDA
MUNICIPAL BOND FUNDS; AS THE FIRST PARAGRAPH UNDER TAX-FREE BOND ON PAGE 14 OF
THE INVESTOR CLASS PROSPECTUS FOR TAX-FREE BOND AND TAX-FREE MONEY MARKET; AND
AS THE SECOND PARAGRAPH UNDER THE FUND MANAGEMENT TEAM ON PAGE 11 OF THE ADVISOR
CLASS PROSPECTUS FOR TAX-FREE BOND.

STEVEN M. PERMUT

Mr. Permut, Senior Vice President and Senior Portfolio Manager, has been a
member of the team since July 2001. He joined American Century in June 1987 and
became a portfolio manager in June 1990. He has a bachelor's degree in business
and geography from State University of New York - Oneonta and an MBA in finance
from Golden Gate University - San Francisco.

THE FOLLOWING IS ADDED AS THE FIRST PARAGRAPH UNDER TAX-FREE MONEY MARKET ON
PAGE 14 OF THE INVESTOR CLASS PROSPECTUS FOR TAX-FREE BOND AND TAX-FREE MONEY
MARKET.

STEVEN M. PERMUT

Mr. Permut, Senior Vice President and Senior Portfolio Manager, has been a
member of the team since June 2003. He joined American Century in June 1987 and
became a portfolio manager in June 1990. He has a bachelor's degree in business
and geography from State University of New York - Oneonta and an MBA in finance
from Golden Gate University - San Francisco.

THE FOLLOWING IS ADDED AS THE SECOND PARAGRAPH UNDER THE FUND MANAGEMENT TEAM ON
PAGE 12 OF THE INVESTOR PROSPECTUS FOR LONG-TERM TAX-FREE.

STEVEN M. PERMUT

THE FOLLOWING ARE ADDED AS THE LAST TWO SENTENCES TO THE FIRST PARAGRAPH UNDER
INVESTING THROUGH A FINANCIAL INTERMEDIARY IN THE LONG-TERM TAX-FREE PROSPECTUS.

The fund is not available for employer-sponsored retirement plans. For more
information regarding employer-sponsored retirement plan types, please see
BUYING AND SELLING FUND SHARES in the statement of additional information.

THE FOLLOWING SENTENCE IS ADDED AS THE LAST SENTENCE TO THE FIRST PARAGRAPH
UNDER CHOOSING A SHARE CLASS IN THE A/B/C CLASS PROSPECTUS FOR THE ARIZONA
MUNICIPAL BOND AND FLORIDA MUNICIPAL BOND FUNDS.

For more information regarding employer-sponsored retirement plan types, please
see BUYING AND SELLING FUND SHARES in the statement of additonal information.

FOR FUNDS WITH AN A CLASS OF SHARES, THE FOLLOWING REPLACES THE SECOND AND
FOURTH BULLETS, RESPECTIVELY, UNDER WAIVERS FOR CERTAIN INVESTORS.

* Broker-dealer sponsored wrap program accounts and/or fee-based accounts
maintained for clients of certain financial intermediaries who have entered
into selling agreements with American Century.

* Employer-sponsored retirement plan purchases. For plans under $1 million
in assets, purchases with sales charges are allowed, but may be subject to
the retirement plan recordkeeper's policies. Refer to BUYING AND SELLING FUND
SHARES in the statement of additional information.

THE FOLLOWING REPLACES THE SECTION MINIMUM INITIAL INVESTMENT AMOUNTS.

MINIMUM INITIAL INVESTMENT AMOUNTS (OTHER THAN INSTITUTIONAL CLASS)

Unless otherwise specified below, the minimum initial investment amount to open
an account is $5,000 ($2,500 for Tax-Free Money Market). Financial
intermediaries may open an account with $250, but may require their clients to
meet different investment minimums. See INVESTING THROUGH A FINANCIAL
INTERMEDIARY for more information. These funds are not available for
employer-sponsored retirement plans.

--------------------------------------------------------------------------------
Broker-dealer sponsored wrap program No minimum
accounts and/or fee-based accounts
--------------------------------------------------------------------------------
Coverdell Education Savings Account (CESA) $5,000(1)(2)(3)
--------------------------------------------------------------------------------
Traditional or Roth IRAs N/A
--------------------------------------------------------------------------------

(1) THE MINIMUM INITIAL INVESTMENT FOR FINANCIAL INTERMEDIARIES IS $250.
FINANCIAL INTERMEDIARIES MAY HAVE DIFFERENT MINIMUMS FOR THEIR CLIENTS.

(2) $2,500 FOR TAX-FREE MONEY MARKET.

(3) TO ESTABLISH A CESA, YOU MUST EXCHANGE FROM ANOTHER AMERICAN CENTURY
CESA OR ROLL OVER A MINIMUM OF $5,000 IN ORDER TO MEET THE FUND'S MINIMUM.

SUBSEQUENT PURCHASES

There is a $50 minimum for subsequent purchases. See WAYS TO MANAGE YOUR ACCOUNT
for more information about making additional investments directly with American
Century. However, there is no subsequent purchase minimum for financial
intermediaries, but financial intermediaries may require their clients to meet
different subsequent purchase requirements.

THE FOLLOWING IS ADDED AS THE THIRD PARAGRAPH UNDER ABUSIVE TRADING PRACTICES ON
PAGE 20 OF THE PROSPECTUS FOR TAX-FREE BOND AND TAX-FREE MONEY MARKET.

For money market funds, American Century anticipates that shareholders will
purchase and sell shares frequently because these funds are designed to offer
investors a liquid investment. Accordingly, American Century has determined that
it is not necessary to monitor trading activity or impose trading restrictions
on money market fund shares and these funds accommodate frequent trading.
However, we reserve the right, in our sole discretion, to modify monitoring and
other practices as necessary to deal with novel or unique abusive trading
practices.

THE FOLLOWING REPLACES THE FIRST SENTENCE OF THE NEXT PARAGRAPH.

For non-money market funds, American Century uses a variety of techniques to
monitor for and detect abusive trading practices.

THE FOLLOWING HEADINGS AND PARAGRAPH ARE ADDED AS THE SECOND PARAGRAPH UNDER
SHARE PRICE ON PAGE 23 OF THE PROSPECTUS FOR TAX-FREE BOND AND TAX-FREE MONEY
MARKET.

TAX-FREE MONEY MARKET

The fund's portfolio securities are valued at amortized cost. This means the
securities are initially valued at their cost when purchased. After the initial
purchase, the difference between the purchase price and the known value at
maturity will be reduced at a constant rate until maturity. This valuation will
be used regardless of the impact of interest rates on the market value of the
security. The board has adopted procedures to ensure that this type of pricing
is fair to the fund's investors.

TAX-FREE BOND

American Century Investment Services, Inc., Distributor

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

SH-SPL-50397 0608

American Century Municipal Trust

STATEMENT OF ADDITIONAL INFORMATION SUPPLEMENT

Supplement dated August 1, 2006 * Statement of Additional Information dated
April 1, 2006

ALL REFERENCES TO "QUALIFIED RETIREMENT PLANS" SHOULD BE REPLACED WITH
"EMPLOYER-SPONSORED RETIREMENT PLANS".

EFFECTIVE MAY 14, 2006, ANTONIO CANOVA RESIGNED FROM THE BOARD OF TRUSTEES.

THE ENTRY FOR CHARLES C.S. PARK IN THE OFFICERS TABLE ON PAGE 28 IS DELETED. THE
FOLLOWING REPLACES THE ENTRY FOR MARYANNE ROEPKE ON PAGE 27.

MARYANNE ROEPKE, 4500 Main Street, Kansas City, MO 64111

YEAR OF BIRTH: 1956

POSITION(S) HELD WITH FUNDS: Acting Chief Compliance Officer, Senior Vice
President, Treasurer and Chief Financial Officer

FIRST YEAR OF SERVICE: 2000

PRINCIPAL OCCUPATION(S) DURING PAST 5 YEARS: Chief Compliance Officer, ACIM,
ACGIM AND ACS (August 2006 to present); Assistant Treasurer, ACC (January 1995
to present). Also serves as: Senior Vice President, ACS; Assistant Treasurer,
ACIM, ACGIM, ACS, ACIS and other ACC subsidiaries

THE FOLLOWING ENTRIES ARE ADDED AS APPROPRIATE TO THE OTHER ACCOUNTS MANAGED'
TABLE ON PAGE 43. INFORMATION PROVIDED AS OF MAY 31, 2006.

OTHER
ACCOUNTS
(E.G.,
REGISTERED OTHER SEPARATE
INVESTMENT POOLED ACCOUNTS
COMPANIES INVESTMENT AND
(E.G., OTHER VEHICLES CORPORATE
AMERICAN (E.G., ACCOUNTS,
CENTURY COMMINGLED INCLUDING
FUNDS AND TRUSTS AND INCUBATION
AMERICAN 529 STRATEGIES
CENTURY - EDUCATION AND
SUBADVISED SAVINGS CORPORATE
FUNDS) PLANS) MONEY)
--------------------------------------------------------------------------------
Arizona Municipal Bond
--------------------------------------------------------------------------------
Steven M. Number of Other 14 0 2
Permut Accounts Managed
------------------------------------------------------------------
Assets in Other $9,280,300,592 N/A $128,988,981
Accounts Managed
--------------------------------------------------------------------------------
Florida Municipal Bond
--------------------------------------------------------------------------------
Steven M. Number of Other 14 0 2
Permut Accounts Managed
------------------------------------------------------------------
Assets in Other $9,293,246,628 N/A $128,988,981
Accounts Managed
--------------------------------------------------------------------------------
Long-Term Tax-Free
--------------------------------------------------------------------------------
Steven M. Number of Other 14 0 2
Permut Accounts Managed
------------------------------------------------------------------
Assets in Other $9,298,958,930 N/A $128,988,981
Accounts Managed
--------------------------------------------------------------------------------
Tax-Free Bond
--------------------------------------------------------------------------------
Steven M. Number of Other 14 0 2
Permut Accounts Managed
------------------------------------------------------------------
Assets in Other $8,665,366,645 N/A $128,988,981
Accounts Managed
--------------------------------------------------------------------------------
Tax-Free Money Market
--------------------------------------------------------------------------------
Steven M. Number of Other 14 0 2
Permut Accounts Managed
------------------------------------------------------------------
Assets in Other $9,065,721,036 N/A $128,988,981
Accounts Managed
--------------------------------------------------------------------------------

THE FOLLOWING ENTRIES ARE ADDED AS APPROPRIATE TO THE OWNERSHIP OF SECURITIES
TABLE ON PAGE 46. INFORMATION PROVIDED AS OF MAY 31, 2006.

AGGREGATE DOLLAR RANGE OF SECURITIES IN FUND
--------------------------------------------------------------------------------
Arizona Municipal Bond
Steven M. Permut(1) A
--------------------------------------------------------------------------------
Florida Municipal Bond
Steven M. Permut(1) A
--------------------------------------------------------------------------------
Long-Term Tax-Free
Steven M. Permut(1) A
--------------------------------------------------------------------------------
Tax-Free Bond
Steven M. Permut(1) A
--------------------------------------------------------------------------------

(1) AMERICAN CENTURY HAS ADOPTED A POLICY THAT, WITH LIMITED EXCEPTIONS,
REQUIRES ITS PORTFOLIO MANAGERS TO MAINTAIN INVESTMENTS IN THE POLICY
PORTFOLIOS THEY OVERSEE. HOWEVER, BECAUSE THIS PORTFOLIO MANAGER SERVES ON
AN INVESTMENT TEAM THAT OVERSEES A NUMBER OF FUNDS IN THE SAME BROAD
INVESTMENT CATEGORY, THE PORTFOLIO MANAGER IS NOT REQUIRED TO INVEST IN
EACH SUCH FUND.

THE FOLLOWING IS ADDED AT THE END OF THE SECTION BUYING AND SELLING FUND SHARES
ON PAGE 57.

American Century considers employer-sponsored retirement plans to include the
following:

• 401(a) plans • 457 plans
• pension plans • KEOGH plans
• profit sharing plans • employer-sponsored 403(b) plans (including self-directed)
• 401k plans • nonqualified deferred compensation plans
• money purchase plans • nonqualified excess benefit plans
• target benefit plans • nonqualified retirement plans
• Taft-Hartley multi-employer pension plans • SIMPLE IRAs
• SERP and "Top Hat" plans • SEP IRAs
• ERISA trusts • SARSEP
• employee benefit trusts

Traditional and Roth IRAs are not considered employer-sponsored retirement
plans. The following table indicates the types of shares that may be purchased
through employer-sponsored retirement plans, Traditional IRAs and Roth IRAs.

TRADITIONAL
EMPLOYER-SPONSORED AND ROTH
RETIREMENT PLANS IRAS
--------------------------------------------------------------------------------
A Class Shares may be purchased @NAV(1) Yes Yes
--------------------------------------------------------------------------------
A Class shares may be purchased Yes, for plans Yes
with dealer concessions and sales charge under $1 million
--------------------------------------------------------------------------------
B Class shares may be purchased(2) No(3) Yes
--------------------------------------------------------------------------------
C Class shares may be purchased Yes, for plans Yes
with dealer concessions and CDSC(2) under $1 million
--------------------------------------------------------------------------------
C Class shares may be purchased Yes No
with no dealer concessions and CDSC(1) (2)
--------------------------------------------------------------------------------
Institutional Class shares may be purchased Yes Yes
--------------------------------------------------------------------------------
Investor Class shares may be purchased Yes Yes
--------------------------------------------------------------------------------
Advisor Class shares may be purchased Yes Yes
--------------------------------------------------------------------------------

(1) REFER TO THE PROSPECTUS REGARDING SALES CHARGES AND CDSC WAIVERS.

(2) REFER TO THE PROSPECTUS FOR MAXIMUM PURCHASE REQUIREMENTS.

(3) SIMPLE IRA PLANS, SEP IRA PLANS AND SARSEP PLANS ESTABLISHED PRIOR TO
AUGUST 1, 2006, MAY MAKE ADDITIONAL PURCHASES.

American Century Investment Services, Inc., Distributor

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

SH-SPL-50410 0608