Cimetidine inhibited nocturnal secretion of acid but only slightly inhibited the nocturnal secretion of pepsin in patients with duodenal ulcer. Administration of cimetidine (200 or 400 mg), together with an anticholinergic drug (poldine), augmented the inhibition of the nocturnal secretion of acid and of pepsin. The combination of an H2-receptor-blocking drug with an anticholinergic drug will have therapeutic application in the management of duodenal ulceration.