Abstract The electric properties of the cells were studied in order to investigate how Na + and Cl − are transported across the gallbladder epithelium. A negative intracellular electric potential of about 60 mV and a near-zero transepithelial potential were measured. By replacing K + on the mucosal or on the serosal side, a paracellular shunt was revealed. By carrying out rapid K + changes on the mucosal side and immediate intracellular potential measurements, the mucosal potential change (Δ Um) coulb be calculated. On this basis, the relationships were obtained between lot [K +]m and Δ Um, with constant [Cl −] and [HCO 3 −] or with these anions replaced by SO 4 2− or with Na + replaced by choline. The results show that the mucosal barrier has a large conductance for K +, a modest conductance for Na + and no-conductance at all for anions. These conclusions were confirmed by the bilateral simultaneous replacement of Na + with choline or of Cl − and HCO 3 − with I − or with SO 4 2−. The intracellular potential is not affected. Thus, both the mucosal and the serosal barrier seem to exhibit similar electric properties. Since the electrical conductance by Cl − is zero through the cell and is insufficient through the shunt to account for the measured net transport of the anion, a coupled neutral transport of Na + and Cl − through the cellular pathway is the most logical explanation of these data.