Extraction rates of lactic acid from aqueous solutions using Alamine 336 dissolved in toluene have been studied by the single drop technique. Interfacial tensions as a function of extractant concentration and initial extraction rates as a function of lactic acid and Alamine 336 concentrations are repotted. Assuming the extraction takes place by an interfacial reaction mechanism, a mass transfer model is proposed for lactic acid reactive extraction. The model assumes a mixed regime, in which the slow diffusion transport of the amine extractant to die inner drop interface, and its protonation at the interface are the rate controlling steps. The influence of a synthetic anionic surfactant, sodium n-dodecyl sulphate, on the extraction process has been also studied. For surfactant concentrations above the specific CMC (critical micelle concentration), the surfactant increases the overall mass-transfer rate up to 40%. The surfactant influence on the extraction kinetics is described on the basis of increasing the interfacial potential and the resulting rise of the proton concentration at the interface.