The effect of Hachimijiogan on cognitive disturbance was investigated using step-through passive avoidance failure techniques : scopolamine-, cycloheximide- and cerebral ischemia-induced amnesia. Pre-acquisition trial administration of Hachimijiogan (0.5 g/kg, p.o.) prolonged the step-through latency reduced by scopolamine and cycloheximide. Hachimijiogan (0.5 and 1.0 g/kg, p.o.) also ameliorated the cerebral ischemia-induced amnesia. Physostigmine (0.1 mg/kg, i.p.) ameliorated all three amnesia models. The ameliorating effects of Hachimijiogan and physostigmine on cycloheximide-induced amnesia were diminished by the combination with scopolamine. These results suggest that Hachimijiogan possesses a wide-ranging pharmacological profile in anti-amnesic actions and that its anti-amnesic activities may be related to the cholinergic neuronal system.