We evaluated the effects of Ginkgo biloba extract (EGb 761) on the cellular immune response of rats with immunosuppression induced by activation of the hypothalamic-pituitary-adrenal (HPA) axis. Groups of five rats were subjected to chronic stress by the application of daily electric shocks (ES) over 7 days. This stress produced a significant decrement in the delayed-type hypersensitivity response (DTH) to dinitrofluorobenzene (DNFB), and a decrease in the proliferation index of splenocytes. Treatment with oral doses of the phytopharmaceutical EGb 761 (100 mg/kg per day over 7 days) restored both the DTH response to DNFB and the proliferation index. EGb 761 has stress-alleviating properties through its moderation of corticosterone levels. It also possesses antioxidant activity that may contribute to its effects on the immune response. Our observations indicate that the phytopharmaceutical EGb 761 possesses immunostimulatory properties.