Exposure to chronic restraint stress in rats and psychosocial stress in humans has been shown to alter cognitive functions such as learning and memory and has been linked to the pathophysiology of mood and anxiety disorders. Antianxiety or sedative agents used in the management of stress have several disadvantages and side effects. Therefore, in this study, we investigated efficacy of a natural medicine, the extract of Ginkgo biloba (EGB 761), in prevention and treatment of the post-stress memory dysfunctions. The results showed that chronic restraint stress (2h for 21 days) or an 'equivalent' dose of exogenous corticosterone (5 mg kg(-1)) decreased re-entry latencies in the passive avoidance situation showing thus impairment of recall. Preventive doses of EGB 761 (100 mg kg(-1)), given 30 min before each restraint stress episode or corticosterone injection, abolished cognitive deficits seen in unprotected rats. There was no influence of stress, corticosterone, and EGB 761 on the acquisition of conditioned avoidance responses (CARs).