Model calculations concerning the membrane potential and ionic fluxes in weak amphoteric polymer membranes have been presented and the results were compared with recent experimental data obtained with a membrane which contains succinyl chitosan as ampholyte and poly(vinyl alcohol) as supporting matrix. The ion transport through the membrane has been described with the aid of the Nernst-Planck equations, and the results obtained explain satisfactorily the observed experimental trends in broad ranges of pH and electrolyte concentration. Also, the model predictions concerning the membrane isoelectric point may be useful for the analysis of future experiments.