Response surface methodology (RSM) is used to optimize the process parameters for the extraction of chromium from aqueous solution of waste sodium dichromate recovered from the pharmaceutical industry wastewater using emulsion liquid membrane technique. The liquid membrane used was composed of kerosene oil as the solvent, Span-80 as the surfactant and potassium hydroxide as internal reagent and Aliquat-336 as carrier. The process parameters, namely feed concentration, pH, internal reagent concentration and surfactant concentration on the extraction of chromium were optimized using Box-Behnken design. The optimum conditions for the extraction of chromium(VI) were: feed concentration (223.55 ppm), pH (2.73), internal reagent concentration (0.72 N) and surfactant concentration (1.91%, w/w). At the optimized condition the maximum chromium extraction was found to be 97.57%. (C) 2008 Elsevier B.V. All rights reserved.