The membrane steady-state current-voltage relations and ionic current developing under membrane potential shifts were investigated in the snail bursting neurons by the clamp method. The steady-state current-voltage relation revealed a nonlinear region. Replacement of sodium by tris-HCl completely removed this region. The membrane hyperpolarization resulted in the development of an outward current which became inactivated after achieving its maximum. The reversal potential of the outward current was about --55 mV. The membrane depolarization led to a slow inward current which also inactivated. The ionic nature of these membrane currents is discussed and a model of slow wave generation in the bursting neurons is suggested.