Effect of AF102B (cis-2-methylspiro-(1,3-oxathiolane-5,3')-quinuclidine) on experimental amnesia was examined using a passive avoidance task in rodents. The amnesia was produced by anti-cholinergic agents, AF64A (intracerebroventricularly) and scopolamine (subcutaneously). AF102B ameliorated the memory deficits in AF64A-treated rats at 0.1-1 mg/kg, i.p. and at 1-5 mg/kg p.o. and in scopolamine-treated mice at 1-10 mg/kg, i.p. These results suggest that AF102B may compensate for central cholinergic defects and could be developed as a possible therapeutic drug for senile dementia of the Alzheimer type.