The electrophoresis of cerebellar granule neurons is observed, and a theoretical model proposed to simulate its electrophoretic behavior. We assume that the surface of a neuronal cell carries dissociable acidic functional groups, and the liquid phase contains a mixed (a:b) + (c:b) electrolyte, where a and c are the valences of cations and b is the valence of anions. The cations of valence c are allowed to bind to dissociated functional groups. The model proposed is readily applicable to the prediction of the surface properties of cerebellar granule neurons such as the density of dissociable functional groups and the equilibrium constant of the dissociation reaction. The applicability of the present model is justified by fitting it to the measured electrophoretic mobility data.