This work focuses on the modeling of solvent-extraction processes carried out in a hollow-fiber membrane contactor (HFC). A resistance-in-series model has been adapted to deal with a conventional solvent or a nonconventional solvent in subcritical conditions. Two kinds of applications have been chosen to test its validity: extraction of ethanol or acetone from an aqueous solution by subcritical carbon dioxide or propane in a single-fiber module, and extraction of sulfur aroma compounds by hexane. Modifications in membrane characteristics and operating parameters have been investigated to determine optimal conditions. Simulations carried out with carbon dioxide have shown that the resistance in the solvent boundary layer is always negligible, whereas, in the case of hexane, the resistance in the aqueous boundary layer is always predominant. For the application with subcritical carbon dioxide, optimal values of feed and solvent velocities have been obtained. These thresholds correspond to the point where the resistance in the membrane becomes predominant. 2005 American Institute of Chemical Engineers