An open comparative trial of nizatidine in the treatment of duodenal ulcer (DU) was carried out with cimetidine as control. Forty-three patients with endoscopically proven DU were recruited into the study. Twenty-three patients were assigned to treatment with nizatidine 300 mg daily and 20 patients (controls) were on cimetidine 800 mg daily. Both groups were comparable in age and sex distribution - age range 21 to 74 years; mean 53.4 years and 43 years in the nizatidine and cimetidine groups respectively. Liver function tests, full blood counts, platelets, urea, electrolytes were done together with endoscopy at four, eight, twelve weeks. In the nizatidine group, 16 patients completed the study whilst 17 patients on cimetidine completed the study. Healing rates at four and eight weeks on nizatidine were 9/16 (56%) and 14/16 (87.5%) respectively. On cimetidine, healing rates at four and eight weeks were 14/17 (80%) and 16/17 (94%) respectively. There was no statistical difference in healing rates between the two groups at four and eight weeks (p = 0.1, p = 0.47). One patient on nizatidine developed urticaria rash which resolved on drug withdrawal. No other adverse clinical or biochemical effects were observed in the cohort after twelve weeks of treatment. Nizatidine is as effective as cimetidine in healing DU at four and eight weeks.