Since many divalent metal ions form more than one complex species with organic extractants, the transport process of such metal ions through a supported liquid membrane (SLM) containing similar extractants as carriers, may involve more than one species. A model has therefore been proposed to describe the rate of transport of more than one metal complex species, using Zn(II)-cyanex 272 system as a typical example, through SLM under different conditions. The overall rate process takes into account the basic interfacial chemical reactions, besides diffusion through the aqueous boundary layer as well as through the organic membrane phase. However, the model is flexible enough to describe the rate of transport of a single permeating species also.