The effects of biota (Biota orientalis ENDL.) on learning impairment produced by bilateral lesion of basal forebrain in mice were studied using step-through and step-down type passive avoidance tasks. Basal forebrain-lesion was generated by applying radiofrequency current. Behavioral experiment, started 15d after the survey, revealed prominent delay in the memory acquisition process in the lesioned mice. The operation also induced memory retention deficit in both learning tests. Chronic oral administration of ethanol extract of biota seeds at doses of 250 and 500 mg/kg/d, from the day of surgery until the end of the behavioral test, dose-dependently improved memory acquisition impairment in the step-down test and memory retention disturbance in both behavioral tasks. The preparation also had a tendency to alleviate memory acquisition impairment in the step-through test. Although precise action mechanisms of biota extract remains speculative, such as what component works on which target, the present results clearly suggest that the preparation affects the learning and memory processes in the central nervous system and improves the impairment of memory acquisition and retention disturbances produced by basal forebrain-lesion.