Why are some trade agreements concluded for a limited period of time while others have the form of evergreen contracts supplemented with an advance termination notice clause? We use a dynamic incomplete contracting model to demonstrate that the time structure of the trade agreement is related to the nature of the underlying trade-related investments (or other types of irreversible resource adjustments). If these investments are lumpy and specialized to trade in a particular homogeneous good, the agreements with the \u85xed term of duration are more likely. The xed-term agreement provides incentives for the initial investment but leaves the parties the exibility to revisit the need for future investment by resorting to renegotiation. If the agreement covers trade in goods or services requiring incremental investments with spillovers of the investment bene\u85ts across industries, there is a lower risk of overinvestment. Therefore, the parties are more likely to choose an evergreen agreement (with an advance termination notice or an escape clause). We show that these predictions are consistent with the econometric evidence on the trade agreements to which the U.S. is a party. We are grateful to Arnaud Costinot, Petros Mavroidis, Marc Melitz and the participants of the Midwest In
