<PAGE> PAGE 1
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000 C000000 0000752177
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000 J000000 U
001 A000000 VANGUARD PRIMECAP FUND
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001 C000000 6106691000
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002 B000000 MALVERN
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<PAGE> PAGE 2
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<PAGE> PAGE 3
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<PAGE> PAGE 4
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<PAGE> PAGE 6
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SIGNATURE SUSAN A TRONEL
TITLE MANAGER
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000752177
<NAME> VANGUARD PRIMECAP FUND
<MULTIPLIER> 1000
<CURRENCY> US
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> DEC-31-1999
<PERIOD-START> JAN-01-1999
<PERIOD-END> DEC-31-1999
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<INVESTMENTS-AT-COST> 9934287
<INVESTMENTS-AT-VALUE> 17933486
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<SHARES-REINVESTED> 21809
<NET-CHANGE-IN-ASSETS> 6701978
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</TABLE>
To the Shareholders and
Trustees of Vanguard PRIMECAP Fund
In planning and performing our audit of the financial statements of
Vanguard PRIMECAP Fund (the "Fund") for the year ended December 31,
1999, we considered its internal control, including control activities for
safeguarding securities, in order to determine our auditing procedures for
the purpose of expressing our opinion on the financial statements and to
comply with the requirements of Form N-SAR, not to provide assurance on
internal control.
The management of the Fund is responsible for establishing and
maintaining internal control. In fulfilling this responsibility, estimates and
judgments by management are required to assess the expected benefits and
related costs of controls. Generally, controls that are relevant to an audit
pertain to the entity's objective of preparing financial statements for
external purposes that are fairly presented in conformity with generally
accepted accounting principles. Those controls include the safeguarding of
assets against unauthorized acquisition, use or disposition.
Because of inherent limitations in internal control, errors or fraud may
occur and not be detected. Also, projection of any evaluation of internal
control to future periods is subject to the risk that it may become inadequate
because of changes in conditions or that the effectiveness of the design and
operation may deteriorate.
Our consideration of internal control would not necessarily disclose all
matters in internal control that might be material weaknesses under
standards established by the American Institute of Certified Public
Accountants. A material weakness is a condition in which the design or
operation of one or more of the internal control components does not reduce
to a relatively low level the risk that misstatements caused by error or fraud
in amounts that would be material in relation to the financial statements
being audited may occur and not be detected within a timely period by
employees in the normal course of performing their assigned functions.
However, we noted no matters involving internal control and its operation,
including controls for safeguarding securities, that we consider to be
material weaknesses as defined above as of December 31, 1999.
This report is intended solely for the information and use of management
and the Board of Trustees of the Fund and the Securities and Exchange
Commission and is not intended to be and should not be used by anyone
other than these specified parties.
PricewaterhouseCoopers LLP
February 2, 2000
