Response surface methodology was applied to optimize the separation Of DL-tryptophan from aqueous solution. DL-tryptophan was extracted into an emulsion liquid membrane containing Aliquat-336 in oleyl alcohol. The carrier concentration (10-30%, by volume). pH (10-14) and initial amino acid concentrations (1-7 mM) were the critical components of the separation optimized. Experiments were performed at 150 rpm stirring rate, for 30 min extraction time with equal volumes of organic and aqueous phases. The response surface equation to predict the extraction yield in the above range of critical components is Y = 100.72 + 31.83x(1) + 0.15x(2) + 3.38x(3) - 21.41x(2)(1) - 5.39x(2)(2) - 7.11x(3)(2) + 1.19x(1)x(2) - 3.26x(1)x(3) - 2.30x(2)x(3) where Y is the response. (extraction yield), Maximum Y (100%) was obtained by employing the following predicted optimum extraction conditions: a pH of 12.46, a carrier concentration of 22.22%, and an initial amino acid concentration of 4.97 mM.