Intracellular Ca2+ is known to activate an early unspecific inward and a potassium outward current in various vertebrate and invertebrate preparations. In the identified neurons B1, B2 and B3 of the buccal ganglia of Helix pomatia an intracellular application of Ca2+ induced a late long-lasting inward current besides the currents mentioned. Ca2+ was injected by ionophoresis or pressure pulses. The long-lasting inward current was reversed at membrane potentials of between -30 and -40 mV, whereas the equilibrium potential of the unspecific inward and potassium outward current was in the range of -20 to +10 mV and -50 to -70 mV, respectively. The late inward current was accompanied by an increase of the membrane conductance and suppressed by the Cl- channel blocker 9-anthracencarbonic acid. The equilibrium potential shifted with changes in the extracellular Cl- concentration. The long-lasting inward current is suggested to be activated by intracellular Ca2+ and to be carried by Cl-.