A prospective double-blind trial was undertaken to determine whether treatment with cimetidine influenced the healing of gastric ulcers in New Zealand patients. Ulcer size and healing was assessed by endoscopic examination. Of the 30 patients who completed the trial, 15 were given cimetidine and 15 placebo. At six weeks, 60% of the patients on cimetidine had healed their ulcers, whereas only 20% of those on the placebo had healed ulcers (P < 0.05). Fewer patients taking cimetidine required antacids for symptom control than those on placebo treatment (P < 0.05). The study confirmed that cimetidine treatment accelerates the healing of gastric ulcers.