Successful investing for long-term funds requires a strategic plan. This is true despite--indeed, because of--the fact that the future is unknowable. The plan must be specific, embodying in concrete terms the best thinking of the board of trustees about the investment pool, its goals and purposes; but it also needs to be sufficiently flexible to guide the board through environments that may be very different from those prevailing at the time of its adoption. This paper reviews the key features of such a plan--the investment policy statement. Since investment policy statements are as varied as the organizations they serve, there is no one-size-fits-all solution. The authors include an appendix with two templates that may serve as examples for those who find it helpful to work from an existing model.