Porocritical extraction was applied to the separation of 1-butanol and acetone from aqueous solutions modeling a typical acetone-butanol-ethanol (ABE) fermentation broth. The efficiency of two lab-scale hollow-fiber membrane contactors of different was studied under various flow rates, solvent-to-feed ratios, and pressure conditions. Global and individual, i.e., tube side, membrane, and shell side mass transfer coefficients were determined. The main contribution to mass transfer resistance was found in the shell side in all cases, and experimentally determined shell side mass transfer coefficients were compared to values predicted by existing correlations.