In aqueous micellar solvent extraction (AMSE), an organic solute is extracted from an aqueous solution across an ultrafiltration membrane into a solvent consisting of an aqueous micellar surfactant solution. The solute crossing the membrane is solubilized in the surfactant micelles, which are retained by the membrane. Phenol was extracted from water into an aqueous solution of sodium dodecyl sulfate (SDS) in hollow fiber membrane contactors of 5 K and 10 K molecular weight cutoff. The objectives were to determine the effect of bulk flow across the membrane on the transfer of phenol, and to measure the extent of back contamination of the wastewater by surfactant. Cocurrent flow of solvent and wastewater with equal transmembrane pressure differences at each end of the module were used to impose uniform bulk flows. Extractions with a range of bulk flowrates across the membrane in either direction yielded smaller overall diffusive mass transfer coefficients than the value with no bulk flow, which was approximately 2 mu m/s. Back contamination of the wastewater by the surfactant was reduced by lowering the CMC of the solvent.