The electrolyte transport through amphoteric nanofiltration membranes is investigated using a model based on the application of the extended Nernst-Planck equation coupled with the electroneutrality condition in the membrane, and the assumption of a Donnan equilibrium at both membrane/solution interfaces. The model gives the possibility to distinguish between the different transport mechanisms, namely, convection, diffusion and electromigration. The influence of ion valence, ion diffusion coefficient and permeate volume flux on the different transport mechanisms and electrolyte retention is presented. All calculations are carried out for a membrane with fixed structural parameters (effective pore radius of 2 nm and effective thickness/porosity ratio of 7 mum).