Aspirin at the dose of 200 mg/kg, administered orally, produced gastric mucosal ulceration in 100% of rats after 4 h. Pretreatment of animals with α-methyldopa at the doses of 25 and 50 mg/kg and/or disulfiram at the doses of 100, 200 and 400 mg/kg, significantly reduced the percentages of rats with gastric ulcerations. It is suggested that the sympathetic nervous system may play a part in the pathogenesis of aspirin-induced gastric ulceration in rats.