<PAGE>
T. ROWE PRICE
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Index Trust, Inc.
T. Rowe Price Equity Index 500 Fund
Supplement to prospectus dated May 1, 1999
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Effective January 1, 2000, Table 3 on page 6 of the prospectus will be revised
with the following to reflect the lower management fee and the extension of the
expense ratio limitation for the Equity Index 500 Fund:
<TABLE>
Table 3 Fees and Expenses of the Funds
<CAPTION> Shareholder fees (fees
paid directly from your Annual fund operating expenses
investment) (expenses that are deducted from fund assets)
Total annual fund
Fund Redemption fee/a/ Small Account fee/b/ Management fee Other expenses operating expenses
<S> <C> <C> <C> <C> <C>
Equity Index 500 0.50% $10 0.15%/c/ 0.29%/c/ 0.44%
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Extended Equity 0.50 10 0.40/d/ -- 0.40
Market Index
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Total Equity Market 0.50 10 0.40/d/ -- 0.40
Index
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<CAPTION>
Fee waiver/expense
Fund reimbursement Net expenses
<S> <C> <C> <S>
Equity Index 500 0.09% 0.35%/c/
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Extended Equity -- 0.40/d/
Market Index ----------------------------------
Total Equity Market -- 0.40/d/
Index
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</TABLE>
/a/On shares purchased and held for less than six months (details under
Contingent Redemption Fees in Pricing Shares and Receiving Sale Proceeds).
/b/A $2.50 quarterly fee is charged for accounts with balances less than
$10,000.
/c/
To limit the fund's expenses, T. Rowe Price contractually obligated itself to
waive its fees and bear any expenses through December 31, 1999, which would
cause the fund's ratio of expenses to average net assets to exceed 0.40%.
Effective January 1, 2000, T. Rowe Price agreed to lower the expense
limitation to 0.35% and extend it for a period of one year through December
31, 2000. Fees waived or expenses paid or assumed under these agreements are
subject to reimbursement to T. Rowe Price by the fund whenever the fund's
expense ratio is below 0.35%; however, no reimbursement will be made after
December 31, 2001, or if it would result in the expense ratio exceeding
0.35%. Any amounts reimbursed will have the effect of increasing fees
otherwise paid by the fund.
/d/ The management fee includes operating expenses.
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The date of this supplement is January 1, 2000.
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C50-041 01/01/00
