Vanguard Federal Money Market Fund | Participant

Risk/Return

Investment Objective

The Fund seeks to provide current income while maintaining liquidity and a stable share price of $1.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold shares of the Fund.

Shareholder Fees (Fees paid directly from your investment)

Shareholder Fees (Vanguard Federal Money Market Fund Participant) Vanguard Federal Money Market Fund	Vanguard Federal Money Market Fund - Investor Shares
Sales charge (load) imposed on purchases	none
Purchase Fee	none
Sales charge (load) imposed on reinvested dividends	none
Redemption Fee	none

Annual Fund Operating Expenses (Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses (Vanguard Federal Money Market Fund Participant) Vanguard Federal Money Market Fund		Vanguard Federal Money Market Fund - Investor Shares
Management Expenses		0.15%
12b-1 Distribution Fee		none
Other Expenses		0.04%
Total Annual Fund Operating Expenses	[1]	0.19%

Example

The following example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invest $10,000 in the Fund's shares. This example assumes that the Fund provides a return of 5% a year and that operating expenses remain as stated in the preceding table. The results apply whether or not you redeem your investment at the end of the given period. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example, No Redemption (Vanguard Federal Money Market Fund Participant) Vanguard Federal Money Market Fund (USD $)	1 YEAR	3 YEAR	5 YEAR	10 YEAR
Vanguard Federal Money Market Fund - Investor Shares	19	61	107	243

Primary Investment Policies

The Fund invests primarily in high-quality, short-term money market instruments. At least 80% of the Fund's assets are invested in securities issued by the U.S. government and its agencies and instrumentalities. Although these securities are high-quality, most of the securities held by the Fund are neither guaranteed by the U.S. Treasury nor supported by the full faith and credit of the U.S. government. To be considered high-quality, a security generally must be rated in one of the two highest credit-quality categories for short-term securities by at least two nationally recognized rating services (or by one, if only one rating service has rated the security). The Fund maintains a dollar-weighted average maturity of 60 days or less and a dollar-weighted average life of 120 days or less.

Primary Risks

The Fund is designed for investors with a low tolerance for risk; however, the Fund's performance could be hurt by:

Income risk, which is the chance that the Fund's income will decline because of falling interest rates. Because the Fund's income is based on short-term interest rates-which can fluctuate significantly over short periods-income risk is expected to be high.

Manager risk, which is the chance that poor security selection will cause the Fund to underperform relevant benchmarks or other funds with a similar investment objective.

Credit risk, which is the chance that the issuer of a security will fail to pay interest and principal in a timely manner, or that negative perceptions of the issuer's ability to make such payments will cause the price of that security to decline. Credit risk should be very low for the Fund because it invests primarily in securities that are considered to be of high quality.

An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. Although the Fund seeks to preserve the value of your investment at $1 per share, it is possible to lose money by investing in the Fund.

Annual Total Returns

The following bar chart and table are intended to help you understand the risks of investing in the Fund. The bar chart shows how the performance of the Fund has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns compare with those of a relevant market index and a comparative benchmark, which have investment characteristics similar to those of the Fund. Returns for the U.S. Government Money Market Funds Average are derived from data provided by Lipper Inc. Keep in mind that the Fund's past performance does not indicate how the Fund will perform in the future. Updated performance information is available on our website at vanguard.com/performance or by calling Vanguard toll-free at 800-662-7447.

Annual Total Returns - Vanguard Federal Money Market Fund Investor Shares

1 The year-to-date return as of the most recent calendar quarter, which ended on September 30, 2011 was 0.01%

During the periods shown in the bar chart, the highest return for a calendar quarter was 1.40% (quarter ended March 31, 2001 ), and the lowest return for a quarter was 0.00% (quarter ended March 31, 2010 ).

Average Annual Total Returns for Periods Ended December 31, 2010

Average Annual Total Returns (Vanguard Federal Money Market Fund Participant) Vanguard Federal Money Market Fund	One Year	Five Years	Ten Years	Index No Deduction for Fees, Expenses, Taxes Participant	Index No Deduction for Fees, Expenses, Taxes Retail
Vanguard Federal Money Market Fund - Investor Shares	0.02%	2.55%	2.35%
Vanguard Federal Money Market Fund - Investor Shares Citigroup 3-Month U.S. Treasury Bill Index	0.13%	2.29%	2.25%	(reflects no deduction for fees or expenses)	(reflects no deduction for fees or expenses)
Vanguard Federal Money Market Fund - Investor Shares U.S. Government Money Market Funds Average	none	2.07%	1.85%

Vanguard Federal Money Market Fund | Retail

Risk/Return

Investment Objective

The Fund seeks to provide current income while maintaining liquidity and a stable share price of $1.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold shares of the Fund.

Shareholder Fees (Fees paid directly from your investment)

Shareholder Fees (Vanguard Federal Money Market Fund Retail) Vanguard Federal Money Market Fund (USD $)	Vanguard Federal Money Market Fund - Investor Shares
Sales charge (load) imposed on purchases	none
Purchase Fee	none
Sales charge (load) imposed on reinvested dividends	none
Redemption Fee	none
Account Service Fee (for fund account balances below $10,000)	20

Annual Fund Operating Expenses (Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses (Vanguard Federal Money Market Fund Retail) Vanguard Federal Money Market Fund		Vanguard Federal Money Market Fund - Investor Shares
Management Expenses		0.15%
12b-1 Distribution Fee		none
Other Expenses		0.04%
Total Annual Fund Operating Expenses	[1]	0.19%

Example

The following example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invest $10,000 in the Fund's shares. This example assumes that the Fund provides a return of 5% a year and that operating expenses remain as stated in the preceding table. The results apply whether or not you redeem your investment at the end of the given period. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example, No Redemption (Vanguard Federal Money Market Fund Retail) Vanguard Federal Money Market Fund (USD $)	1 YEAR	3 YEAR	5 YEAR	10 YEAR
Vanguard Federal Money Market Fund - Investor Shares	19	61	107	243

Primary Investment Policies

The Fund invests primarily in high-quality, short-term money market instruments. At least 80% of the Fund's assets are invested in securities issued by the U.S. government and its agencies and instrumentalities. Although these securities are high-quality, most of the securities held by the Fund are neither guaranteed by the U.S. Treasury nor supported by the full faith and credit of the U.S. government. To be considered high-quality, a security generally must be rated in one of the two highest credit-quality categories for short-term securities by at least two nationally recognized rating services (or by one, if only one rating service has rated the security). The Fund maintains a dollar-weighted average maturity of 60 days or less and a dollar-weighted average life of 120 days or less.

Primary Risks

The Fund is designed for investors with a low tolerance for risk; however, the Fund's performance could be hurt by:

Income risk, which is the chance that the Fund's income will decline because of falling interest rates. Because the Fund's income is based on short-term interest rates-which can fluctuate significantly over short periods-income risk is expected to be high.

Manager risk, which is the chance that poor security selection will cause the Fund to underperform relevant benchmarks or other funds with a similar investment objective.

Credit risk, which is the chance that the issuer of a security will fail to pay interest and principal in a timely manner, or that negative perceptions of the issuer's ability to make such payments will cause the price of that security to decline. Credit risk should be very low for the Fund because it invests primarily in securities that are considered to be of high quality.

An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. Although the Fund seeks to preserve the value of your investment at $1 per share, it is possible to lose money by investing in the Fund.

Annual Total Returns

The following bar chart and table are intended to help you understand the risks of investing in the Fund. The bar chart shows how the performance of the Fund has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns compare with those of a relevant market index and a comparative benchmark, which have investment characteristics similar to those of the Fund. Returns for the U.S. Government Money Market Funds Average are derived from data provided by Lipper Inc. Keep in mind that the Fund's past performance does not indicate how the Fund will perform in the future. Updated performance information is available on our website at vanguard.com/performance or by calling Vanguard toll-free at 800-662-7447.

Annual Total Returns - Vanguard Federal Money Market Fund Investor Shares

1 The year-to-date return as of the most recent calendar quarter, which ended on September 30, 2011 was 0.01%

During the periods shown in the bar chart, the highest return for a calendar quarter was 1.40% (quarter ended March 31, 2001 ), and the lowest return for a quarter was 0.00% (quarter ended March 31, 2010 ).

Average Annual Total Returns for Periods Ended December 31, 2010

Average Annual Total Returns (Vanguard Federal Money Market Fund Retail) Vanguard Federal Money Market Fund	One Year	Five Years	Ten Years	Index No Deduction for Fees, Expenses, Taxes Participant	Index No Deduction for Fees, Expenses, Taxes Retail
Vanguard Federal Money Market Fund - Investor Shares	0.02%	2.55%	2.35%
Vanguard Federal Money Market Fund - Investor Shares Citigroup 3-Month U.S. Treasury Bill Index	0.13%	2.29%	2.25%	(reflects no deduction for fees or expenses)	(reflects no deduction for fees or expenses)
Vanguard Federal Money Market Fund - Investor Shares U.S. Government Money Market Funds Average	none	2.07%	1.85%

Vanguard Prime Money Market Fund | Institutional

Risk/Return

Investment Objective

The Fund seeks to provide current income while maintaining liquidity and a stable share price of $1.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Institutional Shares of the Fund.

Shareholder Fees (Fees paid directly from your investment)

Shareholder Fees (Vanguard Prime Money Market Fund Institutional) Vanguard Prime Money Market Fund	Vanguard Prime Money Market Fund - Institutional Shares
Sales charge (load) imposed on purchases	none
Purchase Fee	none
Sales charge (load) imposed on reinvested dividends	none
Redemption Fee	none

Annual Fund Operating Expenses (Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses (Vanguard Prime Money Market Fund Institutional) Vanguard Prime Money Market Fund		Vanguard Prime Money Market Fund - Institutional Shares
Management Expenses		0.06%
12b-1 Distribution Fee		none
Other Expenses		0.03%
Total Annual Fund Operating Expenses	[1]	0.09%

Example

The following example is intended to help you compare the cost of investing in the Fund's Institutional Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invest $10,000 in the Fund's shares. This example assumes that the Shares provide a return of 5% a year and that operating expenses remain as stated in the preceding table. The results apply whether or not you redeem your investment at the end of the given period. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example, No Redemption (Vanguard Prime Money Market Fund Institutional) Vanguard Prime Money Market Fund (USD $)	1 YEAR	3 YEAR	5 YEAR	10 YEAR
Vanguard Prime Money Market Fund - Institutional Shares	9	29	51	115

Primary Investment Policies

The Fund invests primarily in high-quality, short-term money market instruments, including certificates of deposit, banker's acceptances, commercial paper, and other money market securities. To be considered high-quality, a security generally must be rated in one of the two highest credit-quality categories for short-term securities by at least two nationally recognized rating services (or by one, if only one rating service has rated the security). If unrated, the security must be determined by Vanguard to be of quality equivalent to securities in the two highest credit-quality categories. The Fund invests more than 25% of its assets in securities issued by companies in the financial services industry. The Fund maintains a dollar-weighted average maturity of 60 days or less and a dollar-weighted average life of 120 days or less.

Primary Risks

The Fund is designed for investors with a low tolerance for risk; however, the Fund's performance could be hurt by:

Income risk, which is the chance that the Fund's income will decline because of falling interest rates. Because the Fund's income is based on short-term interest rates-which can fluctuate significantly over short periods-income risk is expected to be high.

Manager risk, which is the chance that poor security selection will cause the Fund to underperform relevant benchmarks or other funds with a similar investment objective.

Credit risk, which is the chance that the issuer of a security will fail to pay interest and principal in a timely manner, or that negative perceptions of the issuer's ability to make such payments will cause the price of that security to decline. Credit risk should be very low for the Fund because it invests primarily in securities that are considered to be of high quality.

Industry concentration risk, which is the chance that there will be overall problems affecting a particular industry. Because the Fund invests more than 25% of its assets in securities issued by companies in the financial services industry, the Fund's performance depends to a greater extent on the overall condition of that industry.

An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. Although the Fund seeks to preserve the value of your investment at $1 per share, it is possible to lose money by investing in the Fund.

Annual Total Returns

The following bar chart and table are intended to help you understand the risks of investing in the Fund. The bar chart shows how the performance of the Fund's Institutional Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Fund's Institutional Shares compare with those of a relevant market index and a comparative benchmark, which have investment characteristics similar to those of the Fund. Returns for the Institutional Money Market Funds Average are derived from data provided by Lipper Inc. Keep in mind that the Fund's past performance does not indicate how the Fund will perform in the future. Updated performance information is available on our website at vanguard.com/performance or by calling Vanguard toll-free at 800-662-7447.

Annual Total Returns - Vanguard Prime Money Market Fund Institutional Shares

1 The year-to-date return as of the most recent calendar quarter, which ended on September 30, 2011 was 0.11%

During the periods shown in the bar chart, the highest return for a calendar quarter was 1.47% (quarter ended March 31, 2001 ), and the lowest return for a quarter was 0.04% (quarter ended March 31, 2010 ).

Average Annual Total Returns for Periods Ended December 31, 2010

Average Annual Total Returns (Vanguard Prime Money Market Fund Institutional) Vanguard Prime Money Market Fund	One Year	Five Years	Ten Years	Index No Deduction for Fees, Expenses, Taxes Institutional
Vanguard Prime Money Market Fund - Institutional Shares	0.20%	2.81%	2.59%
Vanguard Prime Money Market Fund - Institutional Shares Citigroup 3-Month U.S. Treasury Bill Index	0.13%	2.29%	2.25%	(reflects no deduction for fees or expenses)
Vanguard Prime Money Market Fund - Institutional Shares Institutional Money Market Funds Average	0.09%	2.50%	2.25%

Vanguard Prime Money Market Fund | Participant

Risk/Return

Investment Objective

The Fund seeks to provide current income while maintaining liquidity and a stable share price of $1.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Investor Shares of the Fund.

Shareholder Fees (Fees paid directly from your investment)

Shareholder Fees (Vanguard Prime Money Market Fund Participant) Vanguard Prime Money Market Fund	Vanguard Prime Money Market Fund - Investor Shares
Sales charge (load) imposed on purchases	none
Purchase Fee	none
Sales charge (load) imposed on reinvested dividends	none
Redemption Fee	none

Annual Fund Operating Expenses (Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses (Vanguard Prime Money Market Fund Participant) Vanguard Prime Money Market Fund		Vanguard Prime Money Market Fund - Investor Shares
Management Expenses		0.17%
12b-1 Distribution Fee		none
Other Expenses		0.03%
Total Annual Fund Operating Expenses	[1]	0.20%

Example

The following example is intended to help you compare the cost of investing in the Fund's Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invest $10,000 in the Fund's shares. This example assumes that the Shares provide a return of 5% a year and that operating expenses remain as stated in the preceding table. The results apply whether or not you redeem your investment at the end of the given period. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example, No Redemption (Vanguard Prime Money Market Fund Participant) Vanguard Prime Money Market Fund (USD $)	1 YEAR	3 YEAR	5 YEAR	10 YEAR
Vanguard Prime Money Market Fund - Investor Shares	20	64	113	255

Primary Investment Policies

The Fund invests primarily in high-quality, short-term money market instruments, including certificates of deposit, banker's acceptances, commercial paper, and other money market securities. To be considered high-quality, a security generally must be rated in one of the two highest credit-quality categories for short-term securities by at least two nationally recognized rating services (or by one, if only one rating service has rated the security). If unrated, the security must be determined by Vanguard to be of quality equivalent to securities in the two highest credit-quality categories. The Fund invests more than 25% of its assets in securities issued by companies in the financial services industry. The Fund maintains a dollar-weighted average maturity of 60 days or less and a dollar-weighted average life of 120 days or less.

Primary Risks

The Fund is designed for investors with a low tolerance for risk; however, the Fund's performance could be hurt by:

Income risk, which is the chance that the Fund's income will decline because of falling interest rates. Because the Fund's income is based on short-term interest rates-which can fluctuate significantly over short periods-income risk is expected to be high.

Manager risk, which is the chance that poor security selection will cause the Fund to underperform relevant benchmarks or other funds with a similar investment objective.

Credit risk, which is the chance that the issuer of a security will fail to pay interest and principal in a timely manner, or that negative perceptions of the issuer's ability to make such payments will cause the price of that security to decline. Credit risk should be very low for the Fund because it invests primarily in securities that are considered to be of high quality.

Industry concentration risk, which is the chance that there will be overall problems affecting a particular industry. Because the Fund invests more than 25% of its assets in securities issued by companies in the financial services industry, the Fund's performance depends to a greater extent on the overall condition of that industry.

An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. Although the Fund seeks to preserve the value of your investment at $1 per share, it is possible to lose money by investing in the Fund.

Annual Total Returns

The following bar chart and table are intended to help you understand the risks of investing in the Fund. The bar chart shows how the performance of the Fund's Investor Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Fund's Investor Shares compare with those of a relevant market index and a comparative benchmark, which have investment characteristics similar to those of the Fund. Returns for the Money Market Funds Average are derived from data provided by Lipper Inc. Keep in mind that the Fund's past performance does not indicate how the Fund will perform in the future. Updated performance information is available on our website at vanguard.com/performance or by calling Vanguard toll-free at 800-662-7447.

Annual Total Returns - Vanguard Prime Money Market Fund Investor Shares

1 The year-to-date return as of the most recent calendar quarter, which ended on September 30, 2011 was 0.04%

During the periods shown in the bar chart, the highest return for a calendar quarter was 1.43% (quarter ended March 31, 2001 ), and the lowest return for a quarter was 0.01% (quarter ended March 31, 2010 ).

Average Annual Total Returns for Periods Ended December 31, 2010

Average Annual Total Returns (Vanguard Prime Money Market Fund Participant) Vanguard Prime Money Market Fund	One Year	Five Years	Ten Years	Index No Deduction for Fees, Expenses, Taxes Participant	Index No Deduction for Fees, Expenses, Taxes Retail
Vanguard Prime Money Market Fund - Investor Shares	0.06%	2.66%	2.41%
Vanguard Prime Money Market Fund - Investor Shares Citigroup 3-Month U.S. Treasury Bill Index	0.13%	2.29%	2.25%	(reflects no deduction for fees or expenses)	(reflects no deduction for fees or expenses)
Vanguard Prime Money Market Fund - Investor Shares Money Market Funds Average	none	2.16%	1.86%

Vanguard Prime Money Market Fund | Retail

Risk/Return

Investment Objective

The Fund seeks to provide current income while maintaining liquidity and a stable share price of $1.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Investor Shares of the Fund.

Shareholder Fees (Fees paid directly from your investment)

Shareholder Fees (Vanguard Prime Money Market Fund Retail) Vanguard Prime Money Market Fund (USD $)	Vanguard Prime Money Market Fund - Investor Shares
Sales charge (load) imposed on purchases	none
Purchase Fee	none
Sales charge (load) imposed on reinvested dividends	none
Redemption Fee	none
Account Service Fee (for fund account balances below $10,000)	20

Annual Fund Operating Expenses (Expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses (Vanguard Prime Money Market Fund Retail) Vanguard Prime Money Market Fund		Vanguard Prime Money Market Fund - Investor Shares
Management Expenses		0.17%
12b-1 Distribution Fee		none
Other Expenses		0.03%
Total Annual Fund Operating Expenses	[1]	0.20%

Example

The following example is intended to help you compare the cost of investing in the Fund's Investor Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invest $10,000 in the Fund's shares. This example assumes that the Shares provide a return of 5% a year and that operating expenses remain as stated in the preceding table. The results apply whether or not you redeem your investment at the end of the given period. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example, No Redemption (Vanguard Prime Money Market Fund Retail) Vanguard Prime Money Market Fund (USD $)	1 YEAR	3 YEAR	5 YEAR	10 YEAR
Vanguard Prime Money Market Fund - Investor Shares	20	64	113	255

Primary Investment Policies

The Fund invests primarily in high-quality, short-term money market instruments, including certificates of deposit, banker's acceptances, commercial paper, and other money market securities. To be considered high-quality, a security generally must be rated in one of the two highest credit-quality categories for short-term securities by at least two nationally recognized rating services (or by one, if only one rating service has rated the security). If unrated, the security must be determined by Vanguard to be of quality equivalent to securities in the two highest credit-quality categories. The Fund invests more than 25% of its assets in securities issued by companies in the financial services industry. The Fund maintains a dollar-weighted average maturity of 60 days or less and a dollar-weighted average life of 120 days or less.

Primary Risks

The Fund is designed for investors with a low tolerance for risk; however, the Fund's performance could be hurt by:

Income risk, which is the chance that the Fund's income will decline because of falling interest rates. Because the Fund's income is based on short-term interest rates-which can fluctuate significantly over short periods-income risk is expected to be high.

Manager risk, which is the chance that poor security selection will cause the Fund to underperform relevant benchmarks or other funds with a similar investment objective.

Credit risk, which is the chance that the issuer of a security will fail to pay interest and principal in a timely manner, or that negative perceptions of the issuer's ability to make such payments will cause the price of that security to decline. Credit risk should be very low for the Fund because it invests primarily in securities that are considered to be of high quality.

Industry concentration risk, which is the chance that there will be overall problems affecting a particular industry. Because the Fund invests more than 25% of its assets in securities issued by companies in the financial services industry, the Fund's performance depends to a greater extent on the overall condition of that industry.

An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. Although the Fund seeks to preserve the value of your investment at $1 per share, it is possible to lose money by investing in the Fund.

Annual Total Returns

The following bar chart and table are intended to help you understand the risks of investing in the Fund. The bar chart shows how the performance of the Fund's Investor Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Fund's Investor Shares compare with those of a relevant market index and a comparative benchmark, which have investment characteristics similar to those of the Fund. Returns for the Money Market Funds Average are derived from data provided by Lipper Inc. Keep in mind that the Fund's past performance does not indicate how the Fund will perform in the future. Updated performance information is available on our website at vanguard.com/performance or by calling Vanguard toll-free at 800-662-7447.

Annual Total Returns - Vanguard Prime Money Market Fund Investor Shares

1 The year-to-date return as of the most recent calendar quarter, which ended on September 30, 2011 was 0.04%

During the periods shown in the bar chart, the highest return for a calendar quarter was 1.43% (quarter ended March 31, 2001 ), and the lowest return for a quarter was 0.01% (quarter ended March 31, 2010 ).

Average Annual Total Returns for Periods Ended December 31, 2010

Average Annual Total Returns (Vanguard Prime Money Market Fund Retail) Vanguard Prime Money Market Fund	One Year	Five Years	Ten Years	Index No Deduction for Fees, Expenses, Taxes Participant	Index No Deduction for Fees, Expenses, Taxes Retail
Vanguard Prime Money Market Fund - Investor Shares	0.06%	2.66%	2.41%
Vanguard Prime Money Market Fund - Investor Shares Citigroup 3-Month U.S. Treasury Bill Index	0.13%	2.29%	2.25%	(reflects no deduction for fees or expenses)	(reflects no deduction for fees or expenses)
Vanguard Prime Money Market Fund - Investor Shares Money Market Funds Average	none	2.16%	1.86%

[1] Vanguard and the Fund's Board have voluntarily agreed to temporarily limit certain net operating expenses in excess of the Fund's daily yield so as to maintain a zero or positive yield for the Fund. Vanguard and the Fund's Board may terminate the temporary expense limitation at any time.

[1] Vanguard and the Fund's Board have voluntarily agreed to temporarily limit certain net operating expenses in excess of the Fund's daily yield so as to maintain a zero or positive yield for the Fund. Vanguard and the Fund's Board may terminate the temporary expense limitation at any time.

[1] Vanguard and the Fund's Board have voluntarily agreed to temporarily limit certain net operating expenses in excess of the Fund's daily yield so as to maintain a zero or positive yield for the Fund. Vanguard and the Fund's Board may terminate the temporary expense limitation at any time.

[1] Vanguard and the Fund's Board have voluntarily agreed to temporarily limit certain net operating expenses in excess of the Fund's daily yield so as to maintain a zero or positive yield for the Fund. Vanguard and the Fund's Board may terminate the temporary expense limitation at any time.

[1] Vanguard and the Fund's Board have voluntarily agreed to temporarily limit certain net operating expenses in excess of the Fund's daily yield so as to maintain a zero or positive yield for the Fund. Vanguard and the Fund's Board may terminate the temporary expense limitation at any time.