This paper reports a study of the kinetics of zinc extraction from sulfate media with bis(2-ethylhexyl)thiophosphoric acid (D2EHTPA). A cell with a constant interfacial area and with vibrational mixing was used to measure the initial extraction and initial stripping rates under several operating conditions. The results obtained suggest that the extraction process can be described by the reaction mechanism scheme proposed by Ajawin et al. [Ajawin, L.A.; Perez de Ortiz, E.S.; Sawistowski, H. Extraction of zinc by di(2-ethylhexyl) phosporic acid. Chem. Eng. Res. Des. 1983, 61, 62-66.] The reaction rate constants were evaluated by taking into account the nonideality of the aqueous phase. The activity coefficients of the ions in the ZnSO4-H2SO4-Na2SO4 aqueous system were calculated by applying the Pitzer model. The thermodynamic kinetic constants for the forward and backward reactions were found to be 3.1 x 10(-5) m sec(-1) and 1.0 X 10(-6) kmol(-0.5) m(2.5) sec(-1), respectively, at 293 K. The ratio between these rate constants agrees satisfactorily with the thermodynamic equilibrium constant obtained in a previous study.