Dispersion free reactive extraction of L-phenylalanine has been studied using a hollow fiber (HF) membrane module. L-Phenylalanine could be extracted from an aqueous solution having a pH above the pK(a2) value to an organic phase containing Aliquat-336 as the extractant and xylene as the solvent. The solute could be stripped from the organic phase to another aqueous stripping solution of pH maintained below the isoelectric point Of L-phenylalanine. The extraction cum stripping process appear to rely on pH dependence of the distribution coefficient of phenylalanine in the reactive extraction system. The solute recovery and mass transfer rate were found to be appreciable and the experimentally observed low value of height of transfer unit (HTU) indicates good prospect of HF membrane for commercial exploitation. (C) 2003 Published by Elsevier B.V.