The current efficiency, E, of the transport of ions through an ion-penetrable, charged membrane is investigated. Two assumptions often made in the literature, namely, local electroneutrality and Donnan equilibrium, are discussed quantitatively. We show that, if the concentration of fixed charges, C-3, is sufficiently high, the former is appropriate except for the region near the liquid-membrane interface. The deviation from focal electroneutrality is alleviated if Donnan equilibrium can be assumed. In general, if Ci is low, the local electroneutrality is unsatisfactory. Typically, assuming local electroneutrality will overestimate E to an extent on the order of 10% for a high C-3 and 30% for a low C-3. If C-3 is high, the effect of fixed charge distribution on E is marginal, regardless of whether Donnan equilibrium is satisfied. It is significant, however, for the case where C-3 is low. For a fixed total amount of fixed charges, linear fixed charge distribution leads to a higher E than sinusoidal fixed charge distribution.