A generalization of the Faustmann soil rent model is offered which allows for changing rotation lengths over time. Optimization conditions are analyzed and a solution procedure suggested. The variable rotation length model is used to determine whether the Faustmann formulation can be modified or used in situations where prices and production costs vary temporally. Results from both constant and variable rotation models and from an alternative proposed by Bare and Waggener are compared for loblolly pine plantations in the Mid-Atlantic region. Forest Sci. 30:511-523.