The effects of salt type and concentration, of amino acid and surfactant concentrations, of volume ratio, and of solvent on the reverse micellar extraction of tryptophan and phenylalanine at their zwitterionic condition using Aerosol-OT were determined. The effect of solvent on the ion distribution was also examined. The extraction was mainly controlled by the chemical and electrostatic interactions between the amino acids and the surfactant headgroups at the active reverse micellar interface. A simple model which accounts for the effect of different variables and accurately predicts the amino acid solubilization in the reverse micellar phase is proposed.