We studied the effects of human recombinant interleukin-2 (IL-2) on scopolamine-induced amnesia for a passive avoidance response and on scopolamine-induced hyperactivity, in the mouse. The pre-training intraperitoneal administration of the cytokine significantly enhanced the amnesic effect of scopolamine (1.0 mg kg-1 i.p.). Similar effects were observed after repeated administration (2,500 IU/mouse i.p. for 10 days) of the cytokine. In this condition, the treatment with the pro-cholinergic drug acetylcarnitine completely blocked the pro-amnesic effect of IL-2. The cytokine did not affect plasma glucose concentrations, nor induced any change in footshock sensitivity. Intraperitoneal injection of IL-2 significantly enhanced the scopolamine-induced hyperactivity, whereas the cytokine alone was ineffective in modifying locomotor activity. Our results suggest an involvement of the cholinergic system in the neuromodulatory action of IL-2.