Transport of lysine acetylsalicylate (LAS) through supported liquid membrane was investigated using methyl cholate (MC) as extractive agent. Kinetic and thermodynamic models were developed, based on the interaction of the substrate LAS with the extractive agent T, and the diffusion of the formed entity (TS) through the membrane. The experimental results verify the models and enable the determination of macroscopic parameters (permeabilities (P) and initial fluxes (J 0 )), as well as microscopic parameters (association constants (K ass ), and apparent diffusion coefficients (D*)), relating to formed entity (TS) and its diffusion through the membrane organic phase. Parameters such as initial concentration of the substrate in the feed phase, pH of the feed and stripping phases and temperature of the extraction medium were studied. The results obtain indicate that the mechanism of the migration of LAS through the membrane organic phase cannot be a pure diffusion movement but it takes place by successive jumps from one site to another of the extractive agent, via interaction reactions with LAS.