AMERICAN CENTURY INVESTMENT TRUST
N-30D, 1997-10-29
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                                   SEMIANNUAL
                                     REPORT

                             [american century logo]
                                    American
                                 Century(reg.sm)

                                 AUGUST 31, 1997

                                     BENHAM
                                      GROUP

                               Prime Money Market

                               TABLE OF CONTENTS

Report Highlights ........................................................... 1
Our Message to You .......................................................... 2
Market Perspective .......................................................... 3
Performance & Portfolio Information ......................................... 4
Management Q & A ............................................................ 5
Schedule of Investments                                                       7
Statement of Assets and Liabilities .........................................11
Statement of Operations .....................................................12
Statements of Changes in Net Assets .........................................13
Notes to Financial Statements ...............................................14
Financial Highlights ........................................................16
Proxy Voting Results ........................................................17
Retirement Account Information ..............................................18
Background Information
           Investment Philosophy & Policies .................................20
           Comparative Indices ..............................................20
           Lipper Rankings ..................................................20
           Investment Team Leaders ..........................................20
Glossary ....................................................................21

    American  Century  Investments  offers you nearly 70 fund  choices  covering
stocks,  bonds,  money markets,  specialty  investments and blended  portfolios.
We've  organized our funds into three distinct groups to help you identify those
that best fit your needs. These groups, which appear below, are designed to help
simplify your fund decisions.

                 AMERICAN CENTURY INVESTMENTS--FAMILY OF FUNDS
- -------------------------------------------------------------------------------
        Benham                American Century       Twentieth Century(reg. tm)
     Group(reg. tm)                 Group                      Group
- -------------------------------------------------------------------------------
   MONEY MARKET FUNDS         ASSET ALLOCATION &           GROWTH FUNDS
 GOVERNMENT BOND FUNDS          BALANCED FUNDS          INTERNATIONAL FUNDS
 DIVERSIFIED BOND FUNDS   CONSERVATIVE EQUITY FUNDS
  MUNICIPAL BOND FUNDS         SPECIALTY FUNDS
- -------------------------------------------------------------------------------
       Prime
    Money Market


We welcome your comments or questions about this report.
See the back cover for ways to contact us by mail, phone or e-mail.

Twentieth  Century and American Century are registered marks of American Century
Services  Corporation.  Benham Group is a registered  mark of Benham  Management
Corporation.


                                                AMERICAN CENTURY INVESTMENTS


                               REPORT HIGHLIGHTS

MARKET PERSPECTIVE

*   U.S.  money market  yields rose during the six months ended August 31, 1997,
    largely  because of a  short-term  interest  rate  increase  by the  Federal
    Reserve.

*   The Fed  raised  short-term  interest  rates in March to head off  potential
    inflation and slow the rapid pace of economic growth.

*   Money market yields rose sharply in the weeks surrounding the Fed's action.

*   A lack of  inflationary  pressure  during the summer  months led to a modest
    decline in money market yields between May and August.

MANAGEMENT Q & A

*   According to Lipper Analytical  Services,  the fund outperformed the average
    money market fund during the six months ended August 31, 1997.

*   Early in the period,  the fund was positioned  defensively,  with an average
    maturity of 40-45 days,  because of our expectations  for higher  short-term
    rates.

*   The fund's shorter  maturity  enabled it to quickly reflect the Fed interest
    rate increase in March.

*   Because inflation remained in check, we extended the fund's average maturity
    to 60 days in July.

*   The fund  expanded  its  holdings  of  asset-backed  securities,  especially
    commercial paper backed by credit card receivables.

*   Going forward,  we expect short-term interest rates to remain stable through
    the end of 1997, but we may see yields trend higher in early 1998.

*   We plan  to  maintain  the  fund's  current  position  until  we see a clear
    direction for interest rates.

                 PRIME MONEY MARKET

TOTAL RETURNS:                     AS OF 8/31/97
     6 Months                              2.60%*
     1 Year                                5.14%

7-DAY CURRENT YIELD:                       5.19%

NET ASSETS:                        $1.3 billion
     (AS OF 8/31/97)

INCEPTION DATE:                        11/17/93

TICKER SYMBOL:                            BPRXX

* Not annualized.


Many of the investment  terms in this report are defined in the Glossary on page
21.


SEMIANNUAL REPORT                                    REPORT HIGHLIGHTS    1


                              OUR MESSAGE TO YOU

[photo of James E. Stowers III and James M. Benham]

    During the six months  ended  August  31,  1997,  Prime  Money  Market  fund
continued to offer  shareholders very competitive  money market returns.  In the
following pages,  the fund's  investment team provides further details about how
your fund was managed during the period.

    We recently made some changes to the fund's  investment team. Amy O'Donnell,
who has managed the fund since its inception in 1993, has shifted over to manage
American  Century's three government money market funds,  including our flagship
Capital Preservation fund. She has been replaced by John Walsh, a credit analyst
on the Prime fund investment team.

    We also made some important corporate changes. In June, Bill Lyons, American
Century's   chief   operating   officer,   became   president,   assuming   full
responsibility for the company's  day-to-day  operations.  With this change, Jim
Stowers,  Jr. and Jim Stowers III will be able to spend more time developing and
refining new  investment  technologies  and tools that build on and leverage the
proprietary  system they  pioneered  25 years ago. One of our goals is to ensure
that we continue to evolve and  innovate--building  the  investment  tools today
that will help lead us and our investors to success in the next century.

    During the summer, American Century held its largest proxy vote ever, asking
shareholders  to approve  measures to simplify  fund  management  and  eliminate
overlapping  funds.  Most notably,  shareholders  approved a unified fee for all
funds.  In the past,  many of our funds had both a  management  fee and separate
administrative  and transfer  agency  fees.  Under the new fee  structure,  fund
shareholders  pay one  annual  management  fee,  based on a  percentage  of fund
assets.

    In July,  American Century agreed to enter into a business  partnership with
J.P.  Morgan & Co., Inc.,  one of the strongest and most respected  firms in the
financial  services  industry.  J.P.  Morgan will become a significant  minority
owner of American Century Companies,  Inc., the parent company of the investment
manager  of  the  American   Century  family  of  mutual  funds.   Through  this
partnership, we see many opportunities to expand the range of investment choices
and services we offer you. A global  financial  services firm,  J.P.  Morgan has
been in business for more than 150 years, serving institutions,  governments and
individuals with complex financial needs.

    Within  the  framework  of this  new  relationship,  American  Century  will
continue  to  operate as an  independent  company.  No  changes  in your  fund's
investment  managers,  policies  or fees are  anticipated  as a  result  of this
transaction.  American Century's corporate management team remains the same, and
the Stowers family will retain voting control of the company.

    In closing,  we want to reassure you that American Century remains committed
to serving your  investment  needs first and foremost.  Thank you for your trust
and confidence.

Sincerely,

/s/James E. Stowers III                /s/James M. Benham
James E. Stowers III                   James M. Benham
Chief Executive Officer                Vice Chairman
American Century Companies             American Century Companies


2    OUR MESSAGE TO YOU                       AMERICAN CENTURY INVESTMENTS


                              MARKET PERSPECTIVE

[line graph - data below]

Federal Funds Rate vs. Three-Month LIBOR
March 28, 1997 through August 31, 1997

              3-Month LIBOR       Fed Funds Rate Target
2/28/97          5.53906%                 5.25%
3/7/97           5.56250%                 5.25%
3/14/97          5.59766%                 5.25%
3/21/97          5.71875%                 5.25%
3/28/97          5.77344%                 5.50%
4/4/97           5.81250%                 5.50%
4/11/97          5.81641%                 5.50%
4/18/97          5.83594%                 5.50%
4/25/97          5.85156%                 5.50%
5/2/97           5.82031%                 5.50%
5/9/97           5.81250%                 5.50%
5/16/97          5.81641%                 5.50%
5/23/97          5.80469%                 5.50%
5/30/97          5.81250%                 5.50%
6/6/97           5.81250%                 5.50%
6/13/97          5.78125%                 5.50%
6/20/97          5.78125%                 5.50%
6/27/97          5.78125%                 5.50%
7/4/97           5.75000%                 5.50%
7/11/97          5.75000%                 5.50%
7/18/97          5.75000%                 5.50%
7/25/97          5.71875%                 5.50%
8/1/97           5.68750%                 5.50%
8/8/97           5.71875%                 5.50%
8/15/97          5.73828%                 5.50%
8/22/97          5.71875%                 5.50%
8/29/97          5.71875%                 5.50%
Source: DRI/McGraw Hill

MONEY MARKET  YIELDS INCREASED

    Money market  yields rose during the six months  ended August 31, 1997.  The
increase was the direct  result of a short-term  interest  rate  increase by the
Federal  Reserve  in  March.  Although  yields  continued  to rise in the  weeks
following  the Fed rate hike,  they  leveled  off in May and  declined  slightly
throughout the remainder of the period.

    The accompanying  graph  illustrates the change in money market rates during
the  six-month  period.  The graph  features the  three-month  London  Interbank
Offered Rate (LIBOR), a money market rate that most banks and corporations track
when determining the rate they will pay to investors on short-term debt.

FED RAISES SHORT-TERM RATES IN MARCH

    Money market  yields rose sharply in March in  anticipation  of a short-term
interest rate increase by the Federal Reserve.  As expected,  the Fed raised its
federal  funds rate target (the  overnight  lending rate targeted by the Fed for
large loans  between  commercial  banks)  from 5.25% to 5.50%.  It was the Fed's
first rate hike since  February  1995 and was  described  by Fed  officials as a
"pre-emptive strike against inflation."

    In raising rates,  the Fed pointed to evidence of increasing wage pressures,
which are often passed on to consumers in the form of higher prices. The Fed was
also responding to stronger economic  growth--the U.S. economy surged ahead at a
5% annual  rate in the first  quarter  of 1997,  fueled by strong job growth and
increased consumer spending. Economic growth slowed to a 3.3% annual rate in the
second quarter,  but even this level of growth has historically been accompanied
by rising prices.

NO SIGNS OF INFLATION

    Money market yields continued to rise in April,  reflecting  expectations of
rising  inflation  and further Fed  interest  rate  increases.  But the expected
inflation never materialized--the consumer price index rose at an annual rate of
just 1.3% during the  six-month  period.  As a result,  money market yields were
relatively  steady between May and August,  and expectations for future Fed rate
increases disappeared from the market.


SEMIANNUAL REPORT                                 MARKET PERSPECTIVE      3


<TABLE>
<CAPTION>
                      PERFORMANCE & PORTFOLIO INFORMATION

                                                                             AVERAGE ANNUAL RETURNS
                                                  6 MONTHS          1 YEAR           3 YEARS      LIFE OF
FUND(1)
- -------------------------------------------------------------------------------------------------------------------

TOTAL RETURNS AS OF AUGUST 31, 1997

<S>                                                 <C>              <C>              <C>             <C>  
Prime Money Market ...............................  2.60%            5.14%            5.35%           5.06%

90-Day Treasury Bill Index .......................  2.57%            5.16%            5.32%           5.00%(2)

Average Money Market Instrument Fund(3) ..........  2.43%            4.84%            5.00%           4.64%(2)

Fund's Ranking Among Money Market
Instrument Funds(3) ..............................   --          50 out of 294    25 out of 233    10 out of 210

- --------------------------------------------------------------------------------------------------------------------

(1) Inception date was November 17, 1993.

(2) Returns since 11/30/93, the date nearest the fund's inception for which data
    are available.

(3) According to Lipper Analytical Services.
</TABLE>

See pages 20-21 for more information  about returns,  the comparative  index and
Lipper fund rankings.


YIELDS AS OF AUGUST 31, 1997

                                                   7-DAY            7-DAY
                                                  CURRENT         EFFECTIVE
                                                   YIELD            YIELD

Prime Money Market                                 5.19%            5.32%

Yields are defined in the Glossary on page 21.


PORTFOLIO AT A GLANCE
                                                  8/31/97          2/28/97

Number of Securities                                82               71
Weighted Average Maturity                         60 days          54 days
Expense Ratio                                      0.50%*           0.50%

* Annualized.

Money market funds are neither insured nor guaranteed by the U.S. government.

Yields will fluctuate,  and there can be no assurance that the fund will be able
to maintain a stable $1.00 share price.


4    PERFORMANCE & PORTFOLIO INFORMATION      AMERICAN CENTURY INVESTMENTS


                                MANAGEMENT Q&A

    An interview with John Walsh and Denise Tabacco,  portfolio  managers on the
Benham Prime Money Market fund investment team.

HOW DID THE FUND PERFORM?

    The fund  outperformed  the average  money market  fund.  For the six months
ended August 31, 1997,  the fund posted a total return of 2.60%,  compared  with
the 2.43% average return of the 308 "Money Market  Instrument  Funds" tracked by
Lipper  Analytical  Services.  (See the Total Returns table on the previous page
for other fund performance comparisons.)

HOW WAS THE FUND POSITIONED DURING THE SIX-MONTH PERIOD?

    The fund  started  the  period in a  slightly  defensive  position,  with an
average  maturity of around 45 days. We shortened  the fund's  maturity to 35-40
days in May because of our  expectation  for further  interest rate hikes by the
Federal  Reserve.  A shorter  maturity enables the fund to reinvest its maturing
assets more quickly.

    But by July,  it became clear that  inflation was still in check and the Fed
was holding interest rates steady, so we extended the fund's average maturity to
around 60 days. We maintained this position through the end of the period.

WHY IS THE FUND CURRENTLY  HOLDING MORE COMMERCIAL  PAPER THAN IT DID SIX MONTHS
AGO (SEE THE CHART BELOW)?

    There are a couple of reasons. First, most of the new corporate money market
securities  issued  during the summer  were  commercial  paper.  Because of this
increase in supply, commercial paper tended to offer more attractive yields than
other short-term securities.

    Second,  the fund expanded its holdings of asset-backed  securities,  with a
focus on asset-backed  commercial paper. In particular,  the fund purchased part
of a pool of credit card receivables from Citibank.

YOU MENTIONED  INVESTING IN ASSET-BACKED  SECURITIES IN THE LAST REPORT.  WHAT'S
THE ATTRACTION?

    Asset-backed  securities  enable the fund to reach for higher  yields  while
retaining  a high degree of credit  quality.  Asset-backed  securities  are debt
securities that represent  ownership in a pool of assets,  such as auto loans or
credit cards.

    These securities typically have higher yields than commercial paper and CDs,
and they  generally  have very high credit  quality  because  many carry  credit
enhancements. In addition, asset-backed securities are often overcollateralized,
which means the securities  contain more assets than are required to pay off the
debt.

[pie charts]

PORTFOLIO COMPOSITION BY SECURITY TYPE (as of 8/31/97)

Commercial Paper              71%
Floating-Rate Notes           18%*
U.S. Government
  Agency Securities            7%
CDs                            3%
Asset-Backed Securities        1%

PORTFOLIO COMPOSITION BY SECURITY TYPE (as of 2/28/97)

Commercial Paper              61%
Floating-Rate Notes           16%
U.S. Government
  Agency Securities           12%
CDs                           11%*

3% of the fund's floating-rate notes are asset-backed securities.


SEMIANNUAL REPORT                                     MANAGEMENT Q & A    5


                                MANAGEMENT Q&A

DO YOU PLAN TO ADD MORE ASSET-BACKED SECURITIES IN THE FUTURE?

    Yes, but we're taking a very conservative  approach toward these securities.
We've  hired  a  number  of  credit  analysts  who  specialize  in  asset-backed
securities,  and we're  avoiding the more complex  asset-backed  issues that may
have  hidden  credit  risks.  We plan to stick  with  the  most  "plain-vanilla"
asset-backed securities.

LOOKING AHEAD, WHAT'S YOUR OUTLOOK FOR MONEY MARKET RATES?

    We think that money market rates will be fairly  stable  through early 1998.
It's been six months since the Fed's  pre-emptive  interest rate hike, and we've
seen no evidence of  inflationary  pressures since then. We believe that the Fed
won't raise rates again until it sees solid evidence of increasing inflation. As
a result, we think the Fed will be on hold through the end of 1997.

    However,  the next few months  could set the stage for rising  inflation  in
1998.  Wage pressures may be building as a result of sustained low  unemployment
levels.  In addition,  recent  victories  for organized  labor--such  as the UPS
strike--suggest  the  possibility  of rising  wages.  Employment  costs  make up
two-thirds of all business costs, and  corporations  tend to pass on higher wage
costs to consumers by raising prices.

WITH  THAT  OUTLOOK  IN MIND,  HOW WILL YOU  MANAGE  THE FUND  OVER THE NEXT SIX
MONTHS?

    We plan to maintain the fund's  average  maturity at around 60 days until we
see some clear  direction  on  inflation  and  interest  rates.  For now,  we'll
continue to focus on commercial paper for most of the fund's assets,  but we may
look to expand the fund's holdings of floating-rate notes if a Fed rate increase
becomes  more likely.  We also expect to work  closely with our credit  research
staff to uncover value among asset-backed securities.

[pie charts]

PORTFOLIO COMPOSITION BY CREDIT RATING (as of 8/31/97)

A-1+                       80%
A-1                        16%
A-2                         2%
Unrated U.S. Government
  Agency Securities         2%

PORTFOLIO COMPOSITION BY CREDIT RATING (as of 2/28/97)
A-1+                       85%
A-1                        15%

Credit ratings given by Standard & Poor's.


6    MANAGEMENT Q & A                         AMERICAN CENTURY INVESTMENTS


                            SCHEDULE OF INVESTMENTS

AUGUST 31, 1997 (UNAUDITED)

Principal Amount                                                       Value
- --------------------------------------------------------------------------------

COMMERCIAL PAPER(1)

BANKING--26.9%

               $27,000,000  Abbey National North America
                                Corp., 5.36%, 10/8/97              $  26,846,820

                 6,000,000  ABN Amro Bank Canada, 5.39%,
                                9/16/97                                5,986,200

                15,500,000  ABN Amro Bank North America
                                Finance, Inc., 5.38%, 12/15/97        15,249,320

                11,000,000  ANZ (Delaware) Inc., 5.37%,
                                11/4/97                               10,891,662

                10,898,000  Bankers Trust New York Corp.,
                                5.38%, 12/9/97                        10,731,669

                10,000,000  Banque National de Paris (Canada),
                                5.36%, 9/30/97                         9,955,533

                 6,500,000  Banque National de Paris (Canada),
                                5.39%, 12/29/97                        6,380,752

                15,000,000  Banque National de Paris (Canada),
                                5.40%, 1/21/98                        14,672,217

                13,000,000  BIL North America, Inc., 5.38%,
                                12/5/97                               12,809,947

                20,000,000  Chase Manhattan Corp., 5.37%,
                                11/14/97                              19,773,478

                15,000,000  Cibinong International Finance 
                                Company B.V.,
                                5.36%, 9/29/97 (LOC: 
                                Bank of America N.T.
                                & S.A.)                               14,935,600

                13,000,000  Cofco Capital Corp., 5.39%,
                                9/17/97 (LOC: Credit Suisse
                                First Boston)                         12,967,933

                 3,000,000  Cofco Capital Corp., Series B,
                                5.39%, 9/17/97 (Acquired
                                8/19/97, Cost $2,986,636)
                                (LOC: Credit Suisse First
                                Boston)(2)                             2,992,627

                10,000,000      Daewoo International (America) 
                                Corp., 5.37%,
                                10/17/97 (LOC:
                                Credit Suisse First Boston)            9,929,339

                15,000,000  Demir Funding Corporation, 5.36%,
                                10/14/97 (LOC: Bayerische
                                Vereinsbank AG)                       14,901,100

                 5,000,000      Garanti Funding Corporation, 5.40%,
                                1/15/98 (LOC:
                                Bayerische Vereinsbank AG)             4,894,789


Principal Amount                                                       Value
- --------------------------------------------------------------------------------

               $15,000,000  Garanti Funding Corporation,
                                5.57%, 3/4/98 (LOC: Bayerische
                                Vereinsbank AG)                    $  14,572,200

                10,000,000  Garanti Funding Corporation, 5.58%,
                                4/28/98 (LOC: Bayerische
                                Vereinsbank AG)                        9,630,214

                25,000,000  Generale Bank, Inc., 5.39%,
                                9/16/97                               24,941,980

                25,000,000  Generale Bank, Inc., 5.40%, 1/6/98        24,510,027

                 7,055,000  IMI Funding Corp. (U.S.A.), 5.36%,
                                10/1/97                                7,022,430

                25,020,000  IMI Funding Corp. (U.S.A.), 5.40%,
                                2/5/98                                24,414,412

                13,500,000  National Australia Funding
                                (Delaware), Inc., 5.44%, 9/8/97       13,485,563

                10,000,000  National Australia Funding
                                (Delaware), Inc., 5.42%, 9/11/97       9,984,611

                15,000,000  Pemex Capital, Inc., 5.37%,
                                10/22/97 (LOC: Credit Suisse
                                First Boston)                         14,883,125

                20,000,000  Westdeutsche Landesbank
                                Girozentrale, 5.37%, 11/12/97         19,779,200
                                                                 ---------------

                                                                     357,142,748
                                                                 ---------------

DIVERSIFIED COMPANIES--2.2%

                10,000,000  Mitsubishi International Corp.,
                                5.42%, 9/11/97                         9,984,639

                20,000,000  Mitsubishi International Corp.,
                                5.38%, 9/19/97                        19,944,200
                                                                 ---------------

                                                                      29,928,839
                                                                 ---------------

FINANCIAL SERVICES--12.9%

                20,000,000  Aesop Funding Corp., 5.41%,
                                9/12/97 (Acquired 8/1/97,
                                Cost $19,870,500)(2)                  19,966,083

                19,500,000  Dakota Certificates (Citibank),
                                Series 1995-7, 5.43%, 9/10/97
                                (Acquired 6/24/97, Cost
                                $19,264,245)(2)                       19,472,798

                 9,500,000  Dakota Certificates (Citibank),
                                Series 1995-7, 5.38%, 9/22/97
                                (Acquired 8/4/97, Cost
                                $9,478,623)(2)                         9,469,410

                20,000,000  Dakota Certificates (Citibank),
                                Series 1995-7, 5.37%, 11/5/97
                                (Acquired 8/6/97, Cost
                                $19,720,933)(2)                       19,800,667

See Notes to Financial Statements


SEMIANNUAL REPORT                              SCHEDULE OF INVESTMENTS    7


                            SCHEDULE OF INVESTMENTS

AUGUST 31, 1997 (UNAUDITED)

Principal Amount                                                       Value
- --------------------------------------------------------------------------------

               $10,000,000  Dakota Certificates (Citibank),
                                Series 1995-7, 5.37%, 11/10/97
                                (Acquired 8/14/97,
                                Cost $9,864,578)(2)               $    9,892,278

                13,000,000  General Electric Capital Corp.,
                                5.40%, 2/2/98                         12,691,358

                20,000,000  General Electric Capital Services,
                                Inc., 5.36%, 10/6/97                  19,892,278

                27,000,000  General Motors Acceptance Corp.,
                                5.39%, 12/29/97                       26,497,523

                 6,000,000  Hitachi Credit America Corp., 5.42%,
                                9/11/97                                5,990,800

                 5,475,000  Hitachi Credit America Corp., 5.39%,
                                9/18/97                                5,460,470

                10,000,000  Hitachi Credit America Corp., 5.36%,
                                10/6/97                                9,946,236

                11,750,000  Hitachi Credit America Corp., 5.37%,
                                10/28/97                              11,647,305
                                                                 ---------------

                                                                     170,727,206
                                                                 ---------------

HOUSEHOLD AUDIO & VIDEO--1.5%

                20,000,000  Panasonic Finance, Inc., 5.36%,
                                9/29/97 (Acquired 7/7/97,
                                Cost $19,741,467)(2)                  19,913,822
                                                                 ---------------

INSURANCE--1.9%

                13,100,000  American Family Financial
                                Services, Inc., 5.36%, 10/9/97        13,023,947

                13,000,000  General Re Corp., 5.39%,
                                12/31/97                              12,758,370
                                                                 ---------------

                                                                      25,782,317
                                                                 ---------------

MACHINERY--1.5%

                20,000,000  Dover Corp., 5.37%, 9/25/97
                                (Acquired 8/26/97, Cost
                                $19,907,667)(2)                       19,926,133
                                                                 ---------------

METALS & MINING--3.0%

                20,000,000  RTZ America Inc., 5.47%, 9/5/97
                                (Aquired 6/6/97, Cost
                                $19,716,889)(2)                       19,987,555

                10,100,000  RTZ America Inc., 5.36%, 10/8/97
                                (Acquired 7/8/97, Cost
                                $9,957,265)(2)                        10,042,595


Principal Amount                                                       Value
- -------------------------------------------------------------------------------

               $10,000,000  RTZ America Inc., 5.36%,
                                10/14/97 (Acquired 7/14/97,
                                Cost $9,859,189)(2)               $    9,934,186
                                                                  --------------

                                                                      39,964,336
                                                                  --------------

PETROLEUM REFINING--4.5%

                20,000,000  Chevron U.K. Investment PLC,
                                5.48%, 9/4/97                         19,990,650

                30,000,000  Chevron U.K. Investment PLC,
                                5.37%, 10/21/97                       29,770,000

                10,000,000  Petroleo  Brasileiro S.A.,  Series 
                                C & D, 5.37%,
                                10/24/97 (LOC:
                                Barclays Bank PLC)                     9,918,733
                                                                  --------------

                                                                      59,679,383
                                                                  --------------

RETAIL--2.2%

                 9,050,000  Southland Corp., 5.44%, 9/9/97             9,038,899

                12,000,000  Southland Corp., 5.37%, 9/24/97           11,957,833

                 8,150,000  Southland Corp., 5.37%, 11/3/97            8,071,216
                                                                  --------------

                                                                      29,067,948
                                                                  --------------

SECURITY BROKERS & DEALERS--13.7%

                20,000,000  BT Securities Corporation, 5.44%,
                                9/9/97                                19,975,022

                25,000,000  Credit Suisse First Boston, Inc.,
                                5.37%, 10/28/97                       24,781,896

                15,000,000  Credit Suisse First Boston, Inc.,
                                5.40%, 2/2/98                         14,645,800

                15,000,000  Goldman Sachs Group L.P., 5.50%,
                                9/2/97                                14,997,659

                20,000,000  Goldman Sachs Group L.P., 5.37%,
                                11/12/97                              19,778,400

                20,000,000  Merrill Lynch & Co., Inc., 5.49%,
                                9/3/97                                19,993,811

                20,000,000  Merrill Lynch & Co., Inc., 5.37%,
                                11/6/97                               19,797,967

                15,500,000  Merrill Lynch & Co., Inc., 5.38%,
                                11/24/97                              15,299,636

                10,000,000  Morgan Stanley, Dean Witter,
                                Discover & Co., 5.39%, 9/18/97         9,973,744

                22,500,000  Morgan Stanley, Dean Witter,
                                Discover & Co.,  5.36%, 10/9/97       22,369,137
                                                                  --------------
                                                                     181,613,072
                                                                  --------------

See Notes to Financial Statements


8    SCHEDULE OF INVESTMENTS                  AMERICAN CENTURY INVESTMENTS


                            SCHEDULE OF INVESTMENTS

AUGUST 31, 1997 (UNAUDITED)

Principal Amount                                                       Value
- --------------------------------------------------------------------------------

TRUCKING & COURIER SERVICES--0.7%

               $10,000,000  United Parcel Service of America,
                                Inc., 5.38%, 12/12/97             $    9,844,167
                                                                  --------------

TOTAL COMMERCIAL PAPER--71.0%                                        943,589,971
                                                                  --------------

OTHER CORPORATE DEBT

               $25,000,000  Abbey National Treasury Services,
                                VRN, 5.53%, 9/15/97, resets
                                monthly off the 1-month LIBOR
                                minus 0.12% with no caps              24,986,871

                10,000,000      American  Express  Centurion Bank, 
                                VRN,  5.675%, 9/24/97, resets monthly 
                                off the 1-month LIBOR
                                plus 0.05% with no caps               10,001,521

                23,750,000      American  Express  Centurion  Bank,
                                VRN, 5.60%, 9/24/97, resets monthly 
                                off the 1-month LIBOR
                                minus 0.03% with no caps              23,750,000

                13,700,000  First Bank N.A. Minneapolis, VRN,
                                5.59%, 9/17/97, resets monthly
                                off the 1-month LIBOR minus
                                0.04% with no caps                    13,700,000

                50,000,000  General American Life, VRN, 5.87%,
                                9/2/97, resets monthly off the
                                1-month LIBOR plus 0.20% with
                                no caps (Acquired 1/3/97,
                                Cost $50,000,000)(2)                  50,000,000

                47,000,000      Transamerica Occidental Life 
                                Insurance Co., VRN,
                                5.625%,  9/2/97,  resets 
                                monthly off the 1-month
                                LIBOR with no caps 
                                (Acquired 6/30/97, Cost
                                $47,000,000)(2)                       47,000,000

                11,700,000      The Travelers Insurance Company,
                                VRN,  5.68%, 9/9/97,  resets  
                                monthly off the  1-month  LIBOR
                                plus 0.05% with no caps (Acquired 
                                6/9/97, Cost
                                $11,700,000)(2)                       11,700,000

                23,500,000      The Travelers  Insurance  Company,
                                VRN, 5.675%, 9/23/97,  resets 
                                monthly off the 1-month  LIBOR
                                plus 0.05% with no caps (Acquired 
                                5/23/97, Cost $23,500,000)(2)         23,500,000
                                                                  --------------

TOTAL OTHER CORPORATE DEBT--15.4%                                    204,638,392
                                                                  --------------


Principal Amount                                                       Value
- --------------------------------------------------------------------------------

ASSET-BACKED SECURITIES

               $23,500,000  ABSIT 97-C, VRN, 5.65%,
                                9/15/97, resets monthly off the
                                1-month LIBOR with no caps
                                (Acquired 6/11/97, Cost
                                $23,500,000)(2)                    $  23,500,000

                14,000,000  Americredit Automobile Receivables
                                Trust 1997-C, 5.66%, 9/12/98          14,000,000

                14,000,000  Racers Series 1997-MM-8-5, VRN,
                                5.62%, 9/29/97, resets monthly
                                off the 1-month LIBOR minus
                                0.01% with no caps (Acquired
                                8/29/97, Cost $14,000,000)(2)         14,000,000
                                                                  --------------

TOTAL ASSET-BACKED SECURITIES--3.9%                                   51,500,000
                                                                  --------------

U.S. GOVERNMENT AGENCY SECURITIES

                20,000,000  FHLB, 5.685%, 11/20/97                    19,999,315

                40,000,000  FHLB, VRN, 5.80%, 1/30/98                 40,000,000

                15,000,000      FNMA MTN, VRN, 5.45%, 9/3/97,  
                                resets weekly off
                                the 3-month T-Bill rate 
                                plus 0.19% with no caps               15,000,110

                10,000,000      FNMA MTN, VRN, 5.46%, 9/3/97,  
                                resets weekly off
                                the 3-month T-Bill rate 
                                plus 0.20% with no caps               10,000,000
                                                                  --------------

TOTAL U.S. GOVERNMENT AGENCY
SECURITIES--6.4%                                                      84,999,425
                                                                  --------------

CERTIFICATES OF DEPOSIT

                 3,500,000  Rabobank Nederland, 5.99%,
                                3/24/98                                3,502,209

                17,000,000  Societe Generale, 5.70%,
                                12/19/97                              16,994,167

                23,000,000  Societe Generale, 5.63%,
                                12/31/97                              22,998,960
                                                                  --------------

TOTAL CERTIFICATES OF DEPOSIT--3.3%                                   43,495,336
                                                                  --------------

TOTAL INVESTMENT SECURITIES-100.0%                                $1,328,223,124
                                                                  ==============

See Notes to Financial Statements


SEMIANNUAL REPORT                             SCHEDULE OF INVESTMENTS    9


                            SCHEDULE OF INVESTMENTS

NOTES TO SCHEDULE OF INVESTMENTS

FHLB = Federal Home Loan Bank

FNMA = Federal National Mortgage Association

LOC = Letter of Credit

LIBOR = London Interbank Offered Rate

MTN = Medium Term Note

resets= The  frequency  with which a  fixed-income  security's  coupon  changes,
      based on  current  market  conditions  or an  underlying  index.  The more
      frequently  a security  resets,  the less risk the investor is taking that
      the coupon will vary significantly from current market rates.

VRN   =  Variable  Rate  Note.  Interest  reset  date is  indicated  and used in
      calculating  the  weighted  average  portfolio  maturity.  Rate  shown  is
      effective August 31, 1997.

(1) The rates for commercial paper are the yield to maturity at August 31, 1997.

(2) Security was purchased under Rule 144A or Section 4(2) of the Securities Act
    of 1933 and, unless registered under the Act or exempted from  registration,
    may only be sold to qualified institutional  investors.  The aggregate value
    of  restricted  securities  at August  31,  1997,  was  $331,098,154,  which
    represented 24.9% of net assets. Restricted securities which were considered
    illiquid represented 5.5% of net assets.

See Notes to Financial Statements


10    SCHEDULE OF INVESTMENTS                 AMERICAN CENTURY INVESTMENTS


                      STATEMENT OF ASSETS AND LIABILITIES

AUGUST 31, 1997 (UNAUDITED)

ASSETS

Investment securities, at value (Note 1) ............... $1,328,223,124

Cash ...................................................      6,200,413

Interest receivable ....................................      4,130,348
                                                         --------------
                                                          1,338,553,885
                                                         --------------
LIABILITIES

Disbursements in excess of
  demand deposit cash ..................................      3,335,839

Payable for capital shares redeemed ....................      2,250,451

Accrued management fees (Note 2) .......................        571,593

Dividends payable ......................................        374,439

Accrued expenses and other liabilities .................         76,352
                                                         --------------
                                                              6,608,674
                                                         --------------
Net Assets Applicable to
  Outstanding Shares ................................... $1,331,945,211
                                                         ==============

CAPITAL SHARES

Outstanding (Unlimited number
  of shares authorized) ................................  1,332,199,645
                                                         ==============
Net Asset Value Per Share ..............................          $1.00
                                                         ==============
NET ASSETS CONSIST OF:

Capital paid in ........................................ $1,332,199,645

Accumulated undistributed net realized
  loss on investment transactions ......................       (254,434)
                                                         --------------
                                                         $1,331,945,211
                                                         ==============

See Notes to Financial Statements


SEMIANNUAL REPORT                  STATEMENT OF ASSETS AND LIABILITIES    11


                            STATEMENT OF OPERATIONS

FOR THE SIX MONTHS ENDED AUGUST 31, 1997 (UNAUDITED)

INVESTMENT INCOME

Income:

Interest .................................................. $35,220,937
                                                            -----------
Expenses (Note 2):

Investment advisory fees ..................................   2,277,080

Transfer agency fees ......................................     765,989

Administrative fees .......................................     476,721

Printing and postage ......................................     241,103

Custodian fees ............................................      92,192

Telephone expenses ........................................      58,663

Registration and filing fees ..............................      52,224

Trustees' fees and expenses ...............................      28,042

Auditing and legal fees ...................................      23,907

Other operating expenses ..................................      23,710
                                                            -----------
  Total expenses ..........................................   4,039,631

Amount waived .............................................    (894,608)
                                                            -----------
  Net expenses ............................................   3,145,023
                                                            -----------
Net investment income .....................................  32,075,914
                                                            -----------
REALIZED GAIN ON INVESTMENTS (NOTE 3)

Net realized gain on investments ..........................      24,101
                                                            -----------
Net Increase in Net Assets
  Resulting from Operations ............................... $32,100,015
                                                           ============
See Notes to Financial Statements


12    STATEMENT OF OPERATIONS                 AMERICAN CENTURY INVESTMENTS


<TABLE>
<CAPTION>
                      STATEMENTS OF CHANGES IN NET ASSETS

SIX MONTHS ENDED AUGUST 31, 1997 (UNAUDITED)
AND YEAR ENDED FEBRUARY 28, 1997 AND FEBRUARY 29, 1996

                                                    August 31,        February 28,
Increase (Decrease) in Net Assets                      1997               1997

OPERATIONS

<S>                                             <C>                 <C>            
Net investment income ......................... $   32,075,914      $    61,135,898

Net realized gain (loss) on investments .......         24,101            (278,535)
                                                 --------------      --------------
Net increase in net assets
   resulting from operations ..................     32,100,015           60,857,363
                                                 --------------      --------------
DISTRIBUTIONS TO SHAREHOLDERS

From net investment income ....................    (32,075,914)         (61,135,898)
                                                 --------------      --------------
CAPITAL SHARE TRANSACTIONS

Proceeds from shares sold .....................   1,018,726,179       1,722,837,328

Proceeds from reinvestment
  of distributions ............................      30,238,384          58,408,826

Payments for shares redeemed ..................    (929,033,776)     (1,839,630,699)
                                                 --------------      --------------
Net increase (decrease) in net assets
  from capital share transactions .............     119,930,787         (58,384,545)
                                                 --------------      --------------
Net increase (decrease) in net assets .........     119,954,888         (58,663,080)

NET ASSETS

Beginning of period ...........................   1,211,990,323       1,270,653,403
                                                 --------------      --------------
End of period .................................  $1,331,945,211      $1,211,990,323
                                                 ==============      ==============

TRANSACTIONS IN SHARES OF THE FUND

Sold ..........................................   1,018,726,179       1,722,837,328

Issued in reinvestment of distributions .......      30,238,384          58,408,826

Redeemed ......................................    (929,033,776)     (1,839,630,699)
                                                 --------------      --------------
Net increase (decrease) .......................     119,930,787         (58,384,545)
                                                 ==============      ==============
See Notes to Financial Statements
</TABLE>


SEMIANNUAL REPORT                  STATEMENTS OF CHANGES IN NET ASSETS    13


                         NOTES TO FINANCIAL STATEMENTS

AUGUST 31, 1997 (UNAUDITED)

1. ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

    ORGANIZATION--American  Century  Investment  Trust (the Trust) is registered
under the Investment Company Act of 1940 as an open-end  diversified  management
investment company. American Century - Benham Prime Money Market Fund (the Fund)
is the only fund  issued by the  Trust.  The Fund  seeks  the  highest  level of
current  income  consistent  with  preservation  of capital.  The Fund buys high
quality (first tier), U.S. dollar denominated money market instruments and other
short-term obligations of banks,  governments,  and corporations.  The following
significant  accounting  policies,  related to the Fund, are in accordance  with
accounting policies generally accepted in the investment company industry.

    SECURITY   VALUATIONS--Securities   are  valued  at  amortized  cost,  which
approximates  current market value.  When valuations are not readily  available,
securities are valued at fair value as determined in accordance  with procedures
adopted by the Board of Trustees.

    SECURITY  TRANSACTIONS--Security  transactions are accounted for on the date
purchased  or  sold.  Net  realized  gains  and  losses  are  determined  on the
identified cost basis, which is also used for federal income tax purposes.

    INVESTMENT  INCOME--Interest  income is recorded  on the  accrual  basis and
includes  amortization  of discounts  and  premiums.  Discounts and premiums are
amortized daily on a straight-line basis.

    INCOME TAX  STATUS--It is the Fund's policy to distribute all taxable income
and to otherwise qualify as a regulated  investment company under the provisions
of the  Internal  Revenue  Code.  Accordingly,  no  provision  has been made for
federal income taxes.

    DISTRIBUTIONS--Distributions  from net  investment  income are  declared and
credited daily and distributed  monthly. The Fund does not expect to realize any
long-term  capital gains,  and  accordingly,  does not expect to pay any capital
gains distributions.

    SUPPLEMENTARY  INFORMATION--Certain  officers  and trustees of the Trust are
also officers and/or  directors,  and, as a group,  controlling  stockholders of
American Century Companies,  Inc., the parent of the Trust's investment manager,
American Century Investment  Management,  Inc. (ACIM), the Trust's  distributor,
American  Century  Investment  Services,  Inc. and the Trust's  transfer  agent,
American Century Services Corporation (ACSC).

    USE OF ESTIMATES--The preparation of financial statements in conformity with
generally accepted  accounting  principles requires management to make estimates
and assumptions  that affect the reported  amounts of assets and liabilities and
disclosure of  contingent  assets and  liabilities  at the date of the financial
statements  and the reported  amounts of increases  and  decreases in net assets
from  operations  during the  period.  Actual  results  could  differ from these
estimates.


14    NOTES TO FINANCIAL STATEMENTS           AMERICAN CENTURY INVESTMENTS


                         NOTES TO FINANCIAL STATEMENTS

AUGUST 31, 1997 (UNAUDITED)

2. TRANSACTIONS WITH RELATED PARTIES

    The  shareholders of the Fund approved a new management  agreement with ACIM
on July 30,  1997,  effective  August 1, 1997,  which  replaced  the  previously
existing  contracts between the Fund and Benham Management  Corporation and ACSC
for advisory,  administrative and transfer agency services. Under the agreement,
ACIM  provides all services  required by the Fund in exchange for one  "unified"
management  fee.  The annual rate at which this fee is  assessed  is  determined
monthly in a two-step  process:  First,  a fee rate  schedule  is applied to the
assets of all of the funds in the Fund's  investment  category which are managed
by ACIM (the "Investment Category Fee"). The overall investment objective of the
Fund determines its Investment  Category.  The three investment  categories are:
the Money  Market  Fund  Category,  the Bond Fund  Category  and the Equity Fund
Category.  The Prime  Fund is in the  Money  Market  Fund  Category.  Second,  a
separate fee rate  schedule is applied to the assets of all of the funds managed
by ACIM (the "Complex Fee"). The Investment Category Fee and the Complex Fee are
then added to determine the unified  management  fee rate. The management fee is
paid monthly by the Fund based on the Fund's aggregate  average daily net assets
during the previous  month  multiplied by the monthly  management  fee rate. The
annualized Investment Category Fee schedule for the Fund is as follows:

      0.3700% of the first $1 billion  
      0.3270% of the next $1 billion 
      0.2860% of the next $3 billion 
      0.2690% of the next $5 billion 
      0.2580% of the next $15 billion 
      0.2575% of the next $25 billion
      0.2570% of the average daily net assets over $50 billion

    The annualized Complex Fee schedule is as follows:

      0.3100% of the first $2.5 billion 
      0.3000% of the next $7.5 billion 
      0.2985% of the next $15 billion  
      0.2970% of the next $25 billion  
      0.2960% of the next $50 billion 
      0.2950% of the next $100 billion 
      0.2940% of the next $100 billion  
      0.2930% of the next $200 billion 
      0.2920% of the next $250 billion
      0.2910% of the next $500 billion
      0.2900% of the average daily net assets over $1,250 billion

    ACIM has agreed to continue to waive  expenses which exceed 0.50% of average
daily net assets.  Expenses of $675,917,  of which $109,360 were waived by ACIM,
were incurred under the new management  agreement and are included in Investment
Advisory  Fees in the  Statement  of  Operations.  Expenses  under the  previous
agreement,  for the five months ended July 31, 1997, were  $3,363,714,  of which
$785,248  were waived by ACIM.  The ratio of  operating  expenses to average net
assets, net of the amount waived, for the same period was 0.50%.


SEMIANNUAL REPORT                        NOTES TO FINANCIAL STATEMENTS    15


<TABLE>
<CAPTION>
                             FINANCIAL HIGHLIGHTS

For a Share Outstanding Throughout the Years Ended February 28 (except as noted)

                                          1997(1)         1997           1996(2)         1995          1994(3)
PER-SHARE DATA

Net Asset Value,
<S>                                        <C>            <C>             <C>            <C>            <C>  
Beginning of Period .....................  $1.00          $1.00           $1.00          $1.00          $1.00
                                         --------       --------        --------       --------       --------
Income From Investment Operations

  Net Investment Income .................  0.03           0.05            0.06           0.05           0.01
                                         --------       --------        --------       --------       --------
Distributions

  From Net Investment Income ............ (0.03)         (0.05)          (0.06)         (0.05)         (0.01)
                                         --------       --------        --------       --------       --------
Net Asset Value, End of Period ..........  $1.00          $1.00           $1.00          $1.00          $1.00
                                         ========       ========        ========       ========       ========
  Total Return(4) .......................  2.60%          5.04%           5.60%          4.93%          0.96%

RATIOS/SUPPLEMENTAL DATA

Ratio of Operating Expenses
to Average Net Assets ...................0.50%(5)         0.50%           0.48%          0.04%           --

Ratio of Operating Expenses to
Average Net Assets
(Before Expense Waiver) .................0.64%(5)         0.63%           0.62%          0.71%        1.49%(5)

Ratio of Net Investment Income
to Average Net Assets ...................5.11%(5)         4.92%           5.43%          5.28%        3.35%(5)

Ratio of Net Investment Income
to Average Net Assets
(Before Expense Waiver) .................4.97%(5)         4.79%           5.29%          4.61%        1.86%(5)

Net Assets, End
of Period (in thousands) ...............$1,331,945     $1,211,990      $1,270,653     $1,509,863       $75,168


(1) Six months ended August 31, 1997.

(2) Year ended February 29, 1996.

(3) November 17, 1993 (inception) through February 28, 1994.

(4) Total  return   assumes   reinvestment   of  dividends   and  capital  gains
    distributions,  if any.  Total return for periods less than one year are not
    annualized.

(5) Annualized.

See Notes to Financial Statements
</TABLE>


16    FINANCIAL HIGHLIGHTS                   AMERICAN CENTURY INVESTMENTS


                             PROXY VOTING RESULTS

    An annual meeting of shareholders  was held on July 30, 1997, to vote on the
following  proposals.  All of the  proposals  received the required  majority of
votes and were adopted.

    A summary of voting results is listed below each proposal.

PROPOSAL 1:

    To vote on the  selection by the Board of Directors of Coopers & Lybrand LLP
as independent auditors for the Trust.

    For:                                  707,889,037
    Withheld:                              17,468,261
    Abstain:                                9,277,275

PROPOSAL 2:

    To vote on the  approval of a Management  Agreement  with  American  Century
Investment Managment, Inc.

    For:                                  688,718,487
    Against:                               33,656,668
    Abstain:                               12,053,272
    Broker Non-Vote:                          206,146

PROPOSAL 3:

    To vote on the  adoption  of  standardized  investment  limitations  for the
following items:

*   Eliminate the fundamental  investment limitation concerning  diversification
    of investments.

    For:                                  670,961,555
    Against:                               45,887,608
    Abstain:                               17,579,264
    Broker Non-Vote:                          206,146

*   Amend the  fundamental  investment  limitation  concerning  the  issuance of
    senior securities.

    For:                                  670,719,693
    Against:                               46,123,701
    Abstain:                               17,585,033
    Broker Non-Vote:                          206,146

*   Amend the fundamental investment limitation concerning borrowing.

    For:                                  670,236,705
    Against:                               46,575,923
    Abstain:                               17,615,799
    Broker Non-Vote:                          206,146

*   Amend the fundamental investment limitation concerning lending.

    For:                                  670,729,730
    Against:                               46,075,204
    Abstain:                               17,623,493
    Broker Non-Vote:                          206,146

*   Amend the fundamental investment limitation concerning commodities.

    For:                                  672,163,851
    Against:                               44,668,104
    Abstain:                               17,596,472
    Broker Non-Vote:                          206,146


SEMIANNUAL REPORT                                 PROXY VOTING RESULTS    17


                        RETIREMENT ACCOUNT INFORMATION

    As required by law,  any  distributions  you receive from an IRA and certain
403(b)  distributions [not eligible for rollover to an IRA or to another 403(b)]
are subject to federal  income tax  withholding  at the rate of 10% of the total
amount withdrawn,  unless you elect not to have withholding  apply. If you don't
want us to withhold on this amount, you may send us a written notice not to have
the federal  income tax  withheld.  Your written  notice is valid for six months
from the date of receipt at American Century.  Even if you plan to roll over the
amount you withdraw to another tax-deferred  account, the withholding rate still
applies to the withdrawn  amount unless we have received a written notice not to
withhold federal income tax within six months prior to the withdrawal.

    When you plan to  withdraw,  you may make your  election by  completing  our
Exchange/  Redemption form or an IRS Form W-4P. Call American Century for either
form.  Your  written  election  is valid  for only six  months  from the date of
receipt at American Century. You may revoke your election at any time by sending
a written notice to us.

    Remember,  even if you elect not to have income tax withheld, you are liable
for paying income tax on the taxable  portion of your  withdrawal.  If you elect
not to have income tax  withheld or you don't have enough  income tax  withheld,
you may be  responsible  for payment of estimated  tax. You may incur  penalties
under the estimated tax rules if your withholding and estimated tax payments are
not sufficient.

18    RETIREMENT ACCOUNT INFORMATION          AMERICAN CENTURY INVESTMENTS


                                     NOTES


SEMIANNUAL REPORT                                               NOTES    19


                            BACKGROUND INFORMATION

INVESTMENT PHILOSOPHY & POLICIES

    The Benham Group  offers 38  fixed-income  funds,  ranging from money market
funds to long-term bond funds and including both taxable and tax-exempt funds.

    PRIME MONEY  MARKET is a money  market  fund that seeks to provide  interest
income by  investing  in a  diversified  portfolio  of  short-term  money market
securities.  The fund must  maintain a weighted  average  maturity of 90 days or
less.

    An investment in Prime Money Market is neither insured nor guaranteed by the
U.S. government.  Yields will fluctuate,  and there can be no assurance that the
fund will be able to maintain a stable net asset value of $1 per share.

COMPARATIVE INDICES

    The following index is used in the report as a fund performance  comparison.
It is not an investment product available for purchase.

    The 90-DAY  TREASURY BILL INDEX is derived from  secondary  market  interest
rates as published by the Federal Reserve Bank.

LIPPER RANKINGS

    LIPPER  ANALYTICAL  SERVICES,  INC. is an  independent  mutual fund  ranking
service that groups funds according to their investment objectives. Rankings are
based on  average  annual  returns  for each  fund in a given  category  for the
periods indicated. Rankings are not included for periods less than one year.

    The Lipper category for the Prime Money Market fund is:

    MONEY MARKET  INSTRUMENT  FUNDS--funds  that intend to maintain a stable net
asset value and that invest in high-quality  financial  instruments rated in the
top two grades with dollar-weighted average maturities of less than 90 days.

INVESTMENT TEAM LEADERS

Portfolio Managers                John Walsh, Denise Tabacco

Credit Research Director          Greg Afiesh


20    BACKGROUND INFORMATION                  AMERICAN CENTURY INVESTMENTS


                                   GLOSSARY

RETURNS

* TOTAL  RETURN  figures  show the overall  percentage  change in the value of a
hypothetical  investment  in  the  fund  and  assume  that  all  of  the  fund's
distributions are reinvested.

* AVERAGE ANNUAL RETURNS  illustrate the annually  compounded returns that would
have produced the fund's cumulative total returns if the fund's  performance had
been  constant  over the  entire  period.  Average  annual  returns  smooth  out
variations  in a fund's  return;  they are not the same as  fiscal  year-by-year
results.  For  fiscal  year-by-year  returns,  please  refer  to the  "Financial
Highlights" on page 16.

YIELDS

* 7-DAY  CURRENT  YIELD  is  calculated  based  on the  income  generated  by an
investment  in the fund over a seven-day  period and is  expressed  as an annual
percentage rate.

* 7-DAY  EFFECTIVE  YIELD is  calculated  similarly,  although  this  figure  is
slightly  higher than the fund's 7-Day  Current  Yield because of the effects of
compounding.  The 7-Day  Effective  Yield  assumes  that income  earned from the
fund's investments is reinvested and generating additional income.

PORTFOLIO STATISTICS

* NUMBER OF SECURITIES--the  number of different  securities held by a fund on a
given date.

*  WEIGHTED  AVERAGE  MATURITY  (WAM)--a  measurement  of the  sensitivity  of a
fixed-income  portfolio to interest rate changes. WAM indicates the average time
until the securities in the portfolio  mature,  weighted by dollar  amount.  The
longer the WAM, the more interest rate  exposure and  sensitivity  the portfolio
has.

* EXPENSE RATIO--the  operating expenses of the fund,  expressed as a percentage
of average net assets.  Shareholders pay an annual fee to the investment manager
for  investment  advisory  and  management  services.  The expenses and fees are
deducted from fund income, not from each shareholder account. (See Note 2 in the
Notes to Financial Statements.)

TYPES OF MONEY MARKET SECURITIES

* ASSET-BACKED SECURITIES--debt securities that represent ownership in a pool of
receivables, such as credit card debt, auto loans or mortgages.

*  CERTIFICATES  OF DEPOSIT  (CDS)--CDs  represent a bank's  obligation to repay
money deposited with it for a specified  period of time.  Different types of CDs
have different issuers.  For example,  Yankee CDs are issued by U.S. branches of
foreign banks, and Eurodollar CDs are issued in London by Canadian, European and
Japanese banks.

* COMMERCIAL PAPER  (CP)--short-term  debt issued by large corporations to raise
cash and to cover  current  expenses in  anticipation  of future  revenues.  The
maximum  maturity  for CP is 270 days,  although  most CP is issued in a one- to
50-day  maturity  range.  CP rates  generally track those of other widely traded
money market  instruments,  such as Treasury bills and  certificates of deposit,
but they are also influenced by the maturity date and the size and credit rating
of the issuer.

* FLOATING-RATE  NOTES  (FLOATERS)--debt  securities whose interest rates change
when a designated  base rate  changes.  The base rate is often the federal funds
rate, the 90-day Treasury bill rate or the London Interbank Offered Rate (LIBOR)
Floaters are considered  derivatives  because they "derive" their interest rates
from  their   designated   base  rates.   However,   floaters  are  not  "risky"
derivatives--their  behavior is similar to that of their  designated base rates.
The SEC has  recognized  this  similarity  and does not consider  floaters to be
inappropriate investments for money market funds.

* U.S. GOVERNMENT AGENCY  SECURITIES--debt  securities issued by U.S. government
agencies  (such as the Federal Farm Credit Bank and the Federal Home Loan Bank).
Some  agency  securities  are  backed by the full  faith and  credit of the U.S.
government,  while  most  are  guaranteed  only  by the  issuing  agency.  These
securities  are issued with  maturities  ranging  from three months to 30 years.
Money  market  funds  invest  in  these  securities  when  they  have  remaining
maturities of 13 months or less.


SEMIANNUAL REPORT                                          GLOSSARY       21


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INVESTMENT MANAGER
AMERICAN CENTURY INVESTMENT MANAGEMENT, INC.
KANSAS CITY, MISSOURI


THIS  REPORT  AND  THE   STATEMENTS   IT
CONTAINS ARE  SUBMITTED  FOR THE GENERAL
INFORMATION  OF  OUR  SHAREHOLDERS.  THE
REPORT    IS    NOT    AUTHORIZED    FOR
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