An analytical solution is developed for displacement of a nonlinearly sorbing solute in a three-dimensional heterogeneous aquifer. Nonlinear sorption is modeled by means of different isotherm equations including the commonly used Langmuir and Freundlich isotherms, but also the Langmuir-Freundlich, T¿th, and two-site Langmuir isotherms. Evaluation of cleanup times, defined as the times required to reduce the concentration to a given fraction of its initial value, for different isotherms and combinations of input parameters demonstrate the effects of the properties of the isotherms. In particular, the asymptotic behavior as the aqueous concentration approaches zero is important for transport predictions, where Freundlich sorption leads to infinitely increasing cleanup times as the initial plume concentration decreases. The effect of the choice of sorption isotherm, evaluated by using ''best-fit'' parameters for four different isotherms, is found to be large and dependent on heterogeneity for the particular data set considered. ¿ American Geophysical Union 1996.