1. Membrane parameters of an isolated neural cell body have been determined by voltage clamp analysis. Data are expressed as membrane ion-specific conductances, leak conductance, and capacitance.2. Three ionic currents are present: Inward, I(I); and two operationally distinct outward currents, I(K) and I(A). Both outward currents are apparently carried by potassium ions.3. Hodgkin-Huxley-like equations were solved for the discharge of two sequential action potentials in response to a constant stimulus current. The digital computer solutions are compared with action potential data recorded from the investigated cell.4. The computed and experimentally measured relationships between firing frequency and stimulus current intensity are compared and are linear over the same portion of the total frequency range.5. Cell behaviour in the latter part of the interspike interval is dominated by the conductance g(A) while g(Na) and g(K) largely determine the character of the action potential and the initial portion of the interspike interval.6. Prehyperpolarization of the membrane activates g(A) and the membrane response to depolarizing current differs markedly from the response elicited when no prehyperpolarization is imposed.