Electrical activity was recorded in six post-cholecystectomy patients using bipolar serosal electrodes. Three patients were treated with intravenous cimetidine bolus in doses of 200 mg every four hours. Another three patients were treated with intravenous ranitidine bolus in doses of 50 mg every six hours. The frequency and the amplitude of the gastric electrical control activity (ECA) and the incidence of electrical response a activity (ERA) were evaluated before and after the administration of the drugs. The administration of cimetidine and ranitidine did not produce any statistically significant variation in the frequency and amplitude of the gastric ECA and the incidence of ERA. These results show that the effects of the H2-antagonists on gastric electrical activity had no clinical relevance.