485BPOS

File Nos. 002-98772

811-04347

AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION

ON OCTOBER 5, 2012

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

Pre-Effective Amendment No.	¨
Post-Effective Amendment No. 165	x

and

REGISTRATION STATEMENT

UNDER

THE INVESTMENT COMPANY ACT OF 1940

Amendment No. 207 x

GMO TRUST

(Exact Name of Registrant as Specified in Charter)

40 Rowes Wharf, Boston, Massachusetts 02110

(Address of principal executive offices)

617-330-7500

(Registrant’s telephone number, including area code)

with a copy to:

J.B. Kittredge, Esq.	Thomas R. Hiller, Esq.
GMO Trust	Ropes & Gray LLP
40 Rowes Wharf	Prudential Tower
Boston, Massachusetts 02110	800 Boylston Street
	Boston, Massachusetts 02199

(Name and address of agents for service)

It is proposed that this filing will become effective:

x Immediately upon filing pursuant to paragraph (b), or

¨ 60 days after filing pursuant to paragraph (a)(1), or

¨ On             , pursuant to paragraph (b), or

¨ 75 days after filing pursuant to paragraph (a)(2) of Rule 485.

This filing relates only to GMO Risk Premium Fund.

GMO TRUST

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933 (the “Securities Act”) and the Investment Company Act of 1940 (the “1940 Act”), each as amended, the Registrant, GMO Trust, certifies that it meets all of the requirements for effectiveness of this Registration Statement under Rule 485(b) under the Securities Act and has duly caused this Post-Effective Amendment No. 165 under the Securities Act and Amendment No. 207 under the 1940 Act to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Boston and The Commonwealth of Massachusetts, on the 5th day of October, 2012.

GMO Trust
By:	J.B. KITTREDGE*
	J.B. Kittredge
Title:	President; Chief Executive Officer;
	Principal Executive Officer

Pursuant to the requirements of the Securities Act, this Post-Effective Amendment No. 165 to GMO Trust’s Registration Statement under the Securities Act has been signed below by the following persons in the capacities and on the date indicated.

Signatures	Title	Date
J.B. KITTREDGE*	Trustee; President; Chief Executive Officer; Principal Executive Officer	October 5, 2012
J.B. Kittredge
SHEPPARD N. BURNETT*	Treasurer; Chief Financial Officer; Principal Financial and Accounting Officer	October 5, 2012
Sheppard N. Burnett
DONALD W. GLAZER*	Trustee	October 5, 2012
Donald W. Glazer
PETER TUFANO*	Trustee	October 5, 2012
Peter Tufano
PAUL BRAVERMAN*	Trustee	October 5, 2012
Paul Braverman

* By:	/s/ Jason Harrison
	Jason Harrison
	Attorney-in-Fact**

** Pursuant to Powers of Attorney for each of Donald W. Glazer and Peter Tufano filed with the SEC as part of Post-Effective Amendment No. 138 to the Registration Statement under the 1933 Act and Amendment No. 173 to the Registration Statement under the 1940 Act on September 29, 2009, pursuant to Powers of Attorney for each of Sheppard N. Burnett and J.B. Kittredge (in his capacity as President, Chief Executive Officer, and Principal Executive Officer) filed with the SEC as part of Post-Effective Amendment No. 139 to the Registration Statement under the 1933 Act and Amendment No. 174 to the Registration Statement under the 1940 Act on October 30, 2009, and pursuant to Powers of Attorney for each of Paul Braverman and J.B. Kittredge (in his capacity as Trustee) filed with the SEC as part of Post-Effective Amendment No. 140 to the Registration Statement under the 1933 Act and Amendment No. 176 to the Registration Statement under the 1940 Act on April 30, 2010.

GMO TRUST RISK PREMIUM FUND XBRL FILING (OCTOBER 2012)

1

EXHIBIT INDEX

GMO TRUST

Exhibit Ref.	Title of Exhibit
EX-101.INS	XBRL Instance Document
EX-101.SCH	XBRL Taxonomy Extension Schema Document
EX-101.CAL	XBRL Taxonomy Extension Calculation Linkbase
EX.101.DEF	XBRL Taxonomy Extension Definition Linkbase
EX.101.LAB	XBRL Taxonomy Extension Labels Linkbase
EX-101.PRE	XBRL Taxonomy Extension Presentation Linkbase
Other.
1	Certificate of Clerk of the Trust certifying resolution by the Board of Trustees of the Trust required pursuant to Rule 483 under the Securities Act of 1933.

2

EX-99.1

GMO TRUST

CERTIFICATE OF CLERK

I, Jason Harrison, hereby certify that I am the duly elected and acting Clerk of GMO Trust, a Massachusetts business trust (the “Trust”), and do hereby further certify as follows:

Attached hereto as Exhibit A is a true and correct copy of a resolution from the meeting of the Board of Trustees of the Trust (the “Board”) held September 10, 2009 (the “Meeting”). The resolution was duly adopted by the Board at the Meeting. Such resolution has not been modified or rescinded since its adoption and is in full force and effect as of the date hereof.

IN WITNESS WHEREOF, I have hereunto set my hand this 5th day of October, 2012.

By:	/s/ Jason Harrison
Name:	Jason Harrison
Title:	Clerk

Exhibit A

Resolution of the Board – September 10, 2009

Authorization of Power of Attorney

VOTED:

That each of Sheppard N. Burnett and Jason Harrison be, and each of them acting singly hereby is, authorized to sign for J.B. Kittredge, in his name and in the capacity of President, Chief Executive Officer and Principal Executive Officer, on behalf of the Trust, any and all amendments to the Trust’s Registration Statement filed with the Securities and Exchange Commission, pursuant to a power of attorney executed by Mr. Kittredge.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	GMO TRUST
Prospectus Date	rr_ProspectusDate	Sep. 25, 2012
Document Creation Date	dei_DocumentCreationDate	Sep. 25, 2012

XML

GMO Risk Premium Fund

GMO Risk Premium Fund

Investment objective

Total return.

Fees and expenses

The tables below describe the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Shareholder fees
(fees paid directly from your investment)

Shareholder Fees GMO Risk Premium Fund	Class III	Class IV	Class V	Class VI
Purchase premium (as a percentage of amount invested)	0.25%	0.25%	0.25%	0.25%
Redemption fee (as a percentage of amount redeemed)	0.25%	0.25%	0.25%	0.25%

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

Annual Fund Operating Expenses GMO Risk Premium Fund		Class III	Class IV	Class V	Class VI
Management fee	[1]	0.45%	0.45%	0.45%	0.45%
Shareholder service fee	[1]	0.15%	0.10%	0.085%	0.055%
Other expenses	[2]	0.59%	0.59%	0.59%	0.59%
Total annual operating expenses	[2]	1.19%	1.14%	1.13%	1.10%
Expense reimbursement	[1]	(0.59%)	(0.59%)	(0.59%)	(0.59%)
Total annual fund operating expenses after expense reimbursement	[2]	0.60%	0.55%	0.54%	0.51%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

If you sell your shares

Expense Example GMO Risk Premium Fund (USD $)	1 Year	3 Years
Class III	172	430
Class IV	167	414
Class V	166	411
Class VI	163	402

If you do not sell your shares

Expense Example, No Redemption GMO Risk Premium Fund (USD $)	1 Year	3 Years
Class III	146	402
Class IV	141	386
Class V	140	383
Class VI	137	374

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. Because the Fund commenced operations on or following the date of this Prospectus, the Fund’s portfolio turnover rate is not available.

Principal investment strategies

The Manager will seek to achieve the Fund’s investment objective primarily by selling (writing) put options on U.S. and non-U.S. (e.g., Europe, United Kingdom, Japan, Hong Kong, Canada and Australia) stock indices.

The Manager determines which options to sell based on its assessment of the aggregate demand for put options on a given stock index. The Manager expects the Fund to sell put options on a number of stock indices but, from time to time, the Fund may have substantial exposures to a relatively small number of U.S. and/or international stock indices.

The Fund may purchase and sell put and call options of any type, including options on global, regional and country stock indices and options on exchange-traded funds (“ETFs”). The Fund may transact in exchange-traded or over-the-counter (“OTC”) options, and options utilized by the Fund may be cash-settled or physically settled. The Fund is also permitted to invest in other securities which the Manager believes will provide positive total return. The Fund is permitted to invest in options and other securities tied economically to any country in the world, including emerging countries.

The Manager expects that the Fund’s option positions typically will be fully collateralized at the time when the Fund is selling them, which means that the Fund plans to hold sufficient assets to cover the maximum possible loss that the Fund might sustain upon the assignment or exercise of an option sold by the Fund.

For collateral and cash management purposes, the Fund will invest a substantial portion of its assets in shares of GMO U.S. Treasury Fund (another series of the Trust described in a separate prospectus (a “GMO Fund”)), U.S. Treasury bills and other highly rated securities, and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were a diversified investment company. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – Because of the Fund’s emphasis on selling put options on stock indices, the Fund’s shares are expected to decline in value when those indices decline in value. The market price of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. Also, the Fund’s investment strategy of selling put options on stock indices will likely cause the Fund to underperform the equity markets in sharply rising markets.

• Options Risk – There are various risks associated with transactions in exchange-traded and OTC options. The market value of options written by the Fund will be affected by many factors, including changes in the value of underlying securities or indices; changes in the dividend rates of underlying securities (or in the case of indices, the securities comprising such indices); changes in interest rates or exchange rates; changes in the actual or perceived volatility of the stock market and underlying securities; and the remaining time to an option’s expiration.

• Liquidity Risk – Low trading volume, lack of a market maker, large position size, or legal restrictions may limit or prevent the Fund closing its option positions at desirable prices. The Fund’s ability to use options as part of its investment program depends on the liquidity of the markets in those instruments. There can be no assurance that a liquid market will exist when the Fund seeks to close out an option position. If the Fund receives a redemption request and is unable to close out an option that it had sold, the Fund may temporarily be leveraged in relation to its assets.

• Management and Operational Risk – The Fund runs the risk that GMO’s investment techniques will fail to produce desired results. The Fund’s portfolio managers may use quantitative analyses and models, and any imperfections or limitations in those analyses and models could affect the ability of the portfolio managers to implement the strategies they wish to pursue. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and may not include the most recent information about a company or a security. The Fund also runs the risk that deficiencies in GMO’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Focused Investment Risk – Because the Fund can have substantial exposure through a limited number of options contracts and because the Fund’s exposures may relate to a relatively small number of U.S. and/or international stock indices, the Fund is subject to additional risk.

• Non-U.S. Investment Risk – The market prices of many non-U.S. securities fluctuate more than those of U.S. securities. Many non-U.S. markets are less stable, smaller, less liquid, and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Non-U.S. portfolio transactions generally involve higher commission rates, transfer taxes, and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to non-U.S. taxes, including potentially on a retroactive basis, on (i) capital gains it realizes or dividends or interest it receives on non-U.S. securities, (ii) transactions in those securities and (iii) the repatriation of proceeds generated from the sale of those securities. In some non-U.S. markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of non-U.S. issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of investments denominated in non-U.S. currencies.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Market Risk – Fixed Income Securities – The market price of a fixed income investment (e.g., U.S. Treasury bills) can decline due to market-related factors, primarily rising interest rates.

• Credit Risk – Securities issued by the U.S. Treasury generally present minimal credit risk. However, payment of the principal of fixed income securities issued by the U.S. government can be delayed because the guarantee generally only requires payment upon maturity of the securities.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events, as well as other changes in non-U.S. and U.S. economic and political conditions, could adversely affect the value of the Fund’s investments. To the extent that the Fund has focused its investments in the stock index of particular region, adverse geopolitical and other events could have a disproportionate impact on the Fund.

• Large Shareholder Risk – To the extent that a large number of shares of the Fund is held by a single shareholder (e.g., an institutional investor or another GMO Fund) or a group of shareholders with a common investment strategy (e.g., GMO asset allocation accounts), the Fund is subject to the risk that a redemption by those shareholders of all or a large portion of their Fund shares will disrupt the Fund’s operations.

Performance

Because the Fund had not yet completed a full calendar year of operations as of the date of this Prospectus, performance information for the Fund is not included.

[1] Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund for the following expenses to the extent that they are borne by the Fund: audit expenses, fund accounting expenses, pricing service expenses, non-investment related tax expenses, transfer agency expenses, non-investment related legal expenses provided to the Fund by or at the direction of the Manager, federal securities law filing expenses, printing expenses, state and federal registration fees and custody expenses. The Manager also has agreed to waive and/or reduce the Fund's management fees and shareholder service fees to the extent necessary to offset the management fees and shareholder service fees directly or indirectly paid to the Manager as a result of the Fund's direct or indirect investments in other GMO Funds. Management fees and shareholder service fees will not be waived below zero. These waivers and reimbursements will continue through at least September 25, 2013, and may not be terminated prior to this date without the action or consent of the Fund's Board of Trustees.

[2] The amounts represent an annualized estimate of the Fund's operating expenses for its initial fiscal year.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	GMO TRUST
Prospectus Date	rr_ProspectusDate	Sep. 25, 2012
GMO Risk Premium Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	GMO Risk Premium Fund
Objective [Heading]	rr_ObjectiveHeading	Investment objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Total return.
Expense [Heading]	rr_ExpenseHeading	Fees and expenses
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	The tables below describe the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder fees (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	September 25, 2013
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio turnover
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. Because the Fund commenced operations on or following the date of this Prospectus, the Fund’s portfolio turnover rate is not available.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	The amounts represent an annualized estimate of the Fund's operating expenses for its initial fiscal year.
Expense Example [Heading]	rr_ExpenseExampleHeading	Example
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text]	rr_ExpenseExampleByYearCaption	If you sell your shares
Expense Example, No Redemption, By Year, Caption [Text]	rr_ExpenseExampleNoRedemptionByYearCaption	If you do not sell your shares
Strategy [Heading]	rr_StrategyHeading	Principal investment strategies
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Manager will seek to achieve the Fund’s investment objective primarily by selling (writing) put options on U.S. and non-U.S. (e.g., Europe, United Kingdom, Japan, Hong Kong, Canada and Australia) stock indices. The Manager determines which options to sell based on its assessment of the aggregate demand for put options on a given stock index. The Manager expects the Fund to sell put options on a number of stock indices but, from time to time, the Fund may have substantial exposures to a relatively small number of U.S. and/or international stock indices. The Fund may purchase and sell put and call options of any type, including options on global, regional and country stock indices and options on exchange-traded funds (“ETFs”). The Fund may transact in exchange-traded or over-the-counter (“OTC”) options, and options utilized by the Fund may be cash-settled or physically settled. The Fund is also permitted to invest in other securities which the Manager believes will provide positive total return. The Fund is permitted to invest in options and other securities tied economically to any country in the world, including emerging countries. The Manager expects that the Fund’s option positions typically will be fully collateralized at the time when the Fund is selling them, which means that the Fund plans to hold sufficient assets to cover the maximum possible loss that the Fund might sustain upon the assignment or exercise of an option sold by the Fund. For collateral and cash management purposes, the Fund will invest a substantial portion of its assets in shares of GMO U.S. Treasury Fund (another series of the Trust described in a separate prospectus (a “GMO Fund”)), U.S. Treasury bills and other highly rated securities, and unaffiliated money market funds.
Risk [Heading]	rr_RiskHeading	Principal risks of investing in the Fund
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were a diversified investment company. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.” Market Risk – Equity Securities – Because of the Fund’s emphasis on selling put options on stock indices, the Fund’s shares are expected to decline in value when those indices decline in value. The market price of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. Also, the Fund’s investment strategy of selling put options on stock indices will likely cause the Fund to underperform the equity markets in sharply rising markets. Options Risk – There are various risks associated with transactions in exchange-traded and OTC options. The market value of options written by the Fund will be affected by many factors, including changes in the value of underlying securities or indices; changes in the dividend rates of underlying securities (or in the case of indices, the securities comprising such indices); changes in interest rates or exchange rates; changes in the actual or perceived volatility of the stock market and underlying securities; and the remaining time to an option’s expiration. Liquidity Risk – Low trading volume, lack of a market maker, large position size, or legal restrictions may limit or prevent the Fund closing its option positions at desirable prices. The Fund’s ability to use options as part of its investment program depends on the liquidity of the markets in those instruments. There can be no assurance that a liquid market will exist when the Fund seeks to close out an option position. If the Fund receives a redemption request and is unable to close out an option that it had sold, the Fund may temporarily be leveraged in relation to its assets. Management and Operational Risk – The Fund runs the risk that GMO’s investment techniques will fail to produce desired results. The Fund’s portfolio managers may use quantitative analyses and models, and any imperfections or limitations in those analyses and models could affect the ability of the portfolio managers to implement the strategies they wish to pursue. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and may not include the most recent information about a company or a security. The Fund also runs the risk that deficiencies in GMO’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations. Focused Investment Risk – Because the Fund can have substantial exposure through a limited number of options contracts and because the Fund’s exposures may relate to a relatively small number of U.S. and/or international stock indices, the Fund is subject to additional risk. Non-U.S. Investment Risk – The market prices of many non-U.S. securities fluctuate more than those of U.S. securities. Many non-U.S. markets are less stable, smaller, less liquid, and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Non-U.S. portfolio transactions generally involve higher commission rates, transfer taxes, and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to non-U.S. taxes, including potentially on a retroactive basis, on (i) capital gains it realizes or dividends or interest it receives on non-U.S. securities, (ii) transactions in those securities and (iii) the repatriation of proceeds generated from the sale of those securities. In some non-U.S. markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of non-U.S. issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries. Currency Risk – Fluctuations in exchange rates can adversely affect the market value of investments denominated in non-U.S. currencies. Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other risks, including market risk, liquidity risk, currency risk and counterparty risk. Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. Market Risk – Fixed Income Securities – The market price of a fixed income investment (e.g., U.S. Treasury bills) can decline due to market-related factors, primarily rising interest rates. Credit Risk – Securities issued by the U.S. Treasury generally present minimal credit risk. However, payment of the principal of fixed income securities issued by the U.S. government can be delayed because the guarantee generally only requires payment upon maturity of the securities. Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events, as well as other changes in non-U.S. and U.S. economic and political conditions, could adversely affect the value of the Fund’s investments. To the extent that the Fund has focused its investments in the stock index of particular region, adverse geopolitical and other events could have a disproportionate impact on the Fund. Large Shareholder Risk – To the extent that a large number of shares of the Fund is held by a single shareholder (e.g., an institutional investor or another GMO Fund) or a group of shareholders with a common investment strategy (e.g., GMO asset allocation accounts), the Fund is subject to the risk that a redemption by those shareholders of all or a large portion of their Fund shares will disrupt the Fund’s operations.
Risk Lose Money [Text]	rr_RiskLoseMoney	Many factors can affect this value, and you may lose money by investing in the Fund.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were a diversified investment company.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	Because the Fund had not yet completed a full calendar year of operations as of the date of this Prospectus, performance information for the Fund is not included.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	Because the Fund had not yet completed a full calendar year of operations as of the date of this Prospectus, performance information for the Fund is not included.
GMO Risk Premium Fund | Class III
Risk/Return:	rr_RiskReturnAbstract
Purchase premium (as a percentage of amount invested)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	0.25%
Redemption fee (as a percentage of amount redeemed)	rr_RedemptionFeeOverRedemption	0.25%
Management fee	rr_ManagementFeesOverAssets	0.45%	[1]
Shareholder service fee	rr_DistributionOrSimilarNon12b1FeesOverAssets	0.15%	[1]
Other expenses	rr_OtherExpensesOverAssets	0.59%	[2]
Total annual operating expenses	rr_ExpensesOverAssets	1.19%	[2]
Expense reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.59%)	[1]
Total annual fund operating expenses after expense reimbursement	rr_NetExpensesOverAssets	0.60%	[2]
1 Year	rr_ExpenseExampleYear01	172
3 Years	rr_ExpenseExampleYear03	430
1 Year	rr_ExpenseExampleNoRedemptionYear01	146
3 Years	rr_ExpenseExampleNoRedemptionYear03	402
GMO Risk Premium Fund | Class IV
Risk/Return:	rr_RiskReturnAbstract
Purchase premium (as a percentage of amount invested)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	0.25%
Redemption fee (as a percentage of amount redeemed)	rr_RedemptionFeeOverRedemption	0.25%
Management fee	rr_ManagementFeesOverAssets	0.45%	[1]
Shareholder service fee	rr_DistributionOrSimilarNon12b1FeesOverAssets	0.10%	[1]
Other expenses	rr_OtherExpensesOverAssets	0.59%	[2]
Total annual operating expenses	rr_ExpensesOverAssets	1.14%	[2]
Expense reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.59%)	[1]
Total annual fund operating expenses after expense reimbursement	rr_NetExpensesOverAssets	0.55%	[2]
1 Year	rr_ExpenseExampleYear01	167
3 Years	rr_ExpenseExampleYear03	414
1 Year	rr_ExpenseExampleNoRedemptionYear01	141
3 Years	rr_ExpenseExampleNoRedemptionYear03	386
GMO Risk Premium Fund | Class V
Risk/Return:	rr_RiskReturnAbstract
Purchase premium (as a percentage of amount invested)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	0.25%
Redemption fee (as a percentage of amount redeemed)	rr_RedemptionFeeOverRedemption	0.25%
Management fee	rr_ManagementFeesOverAssets	0.45%	[1]
Shareholder service fee	rr_DistributionOrSimilarNon12b1FeesOverAssets	0.085%	[1]
Other expenses	rr_OtherExpensesOverAssets	0.59%	[2]
Total annual operating expenses	rr_ExpensesOverAssets	1.13%	[2]
Expense reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.59%)	[1]
Total annual fund operating expenses after expense reimbursement	rr_NetExpensesOverAssets	0.54%	[2]
1 Year	rr_ExpenseExampleYear01	166
3 Years	rr_ExpenseExampleYear03	411
1 Year	rr_ExpenseExampleNoRedemptionYear01	140
3 Years	rr_ExpenseExampleNoRedemptionYear03	383
GMO Risk Premium Fund | Class VI
Risk/Return:	rr_RiskReturnAbstract
Purchase premium (as a percentage of amount invested)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	0.25%
Redemption fee (as a percentage of amount redeemed)	rr_RedemptionFeeOverRedemption	0.25%
Management fee	rr_ManagementFeesOverAssets	0.45%	[1]
Shareholder service fee	rr_DistributionOrSimilarNon12b1FeesOverAssets	0.055%	[1]
Other expenses	rr_OtherExpensesOverAssets	0.59%	[2]
Total annual operating expenses	rr_ExpensesOverAssets	1.10%	[2]
Expense reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.59%)	[1]
Total annual fund operating expenses after expense reimbursement	rr_NetExpensesOverAssets	0.51%	[2]
1 Year	rr_ExpenseExampleYear01	163
3 Years	rr_ExpenseExampleYear03	402
1 Year	rr_ExpenseExampleNoRedemptionYear01	137
3 Years	rr_ExpenseExampleNoRedemptionYear03	374

[1] Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund for the following expenses to the extent that they are borne by the Fund: audit expenses, fund accounting expenses, pricing service expenses, non-investment related tax expenses, transfer agency expenses, non-investment related legal expenses provided to the Fund by or at the direction of the Manager, federal securities law filing expenses, printing expenses, state and federal registration fees and custody expenses. The Manager also has agreed to waive and/or reduce the Fund's management fees and shareholder service fees to the extent necessary to offset the management fees and shareholder service fees directly or indirectly paid to the Manager as a result of the Fund's direct or indirect investments in other GMO Funds. Management fees and shareholder service fees will not be waived below zero. These waivers and reimbursements will continue through at least September 25, 2013, and may not be terminated prior to this date without the action or consent of the Fund's Board of Trustees.

[2] The amounts represent an annualized estimate of the Fund's operating expenses for its initial fiscal year.

XML

Document and Entity Information	12 Months Ended
	Sep. 25, 2012
Risk/Return:
Document Type	485BPOS
Document Period End Date	Sep. 25, 2012
Registrant Name	GMO TRUST
Central Index Key	0000772129
Amendment Flag	false
Document Creation Date	Sep. 25, 2012
Document Effective Date	Sep. 25, 2012
Prospectus Date	Sep. 25, 2012