Light duration and intensity influence classical conditioning inHermissendathrough their effects on the light-induced currents. Furthermore, the contribution of voltage-dependent potassium currents to the long-lasting depolarization in type B photoreceptors depends on light-induced currents active at resting potentials. Thus, the present study measures the effect of holding potential, duration, and intensity on the light-induced currents in discontinuous single-electrode voltage clamp mode. Three distinct current components are distinguished by their temporal and voltage characteristics and sensitivity to pharmacological agents. One current component is a transient sodium current,INalgt; another is a plateau sodium current,Iplateau, which persists for the duration of the light stimulus. Substitution of trimethylammonium chloride for sodium reduces both currents equally, suggesting thatIplateaurepresents partial inactivation ofINalgt. The third current component is a prolonged reduction in potassium currents,IKlgt; it is accompanied by an increase in input resistance, and it appears at potentials close to rest. An increase in light duration or intensity causes an increase in the peak conductance of bothINalgtandIKlgt. Latency ofINalgtis decreased by intensity, whereas rise time is increased by duration. An increase in light duration or intensity causes an increase in the time-to-peak and duration ofIKlgt. Characteristics of these currents suggest thatIKlgtis responsible for the long-lasting depolarization seen after light termination, and thus plays a role in classical conditioning.