In a double-blind, randomized, comparative trial of the prokinetic drug cisapride and the H2-blocker cimetidine, mucosal healing and changes in symptoms of gastroesophageal reflux were evaluated in patients with erosive reflux esophagitis. The patients were treated with either cisapride, 10 mg four times a day (N = 36) or cimetidine, 400 mg four times a day (N = 37) for six weeks, or for 12 weeks if mucosal healing was not obtained by week 6. Upon entry, two thirds of the patients in each group had grade I (Savary-Miller) esophagitis, and the remainder grade II or III. At the end of treatment, endoscopy showed mucosal healing in 56% (38-72%; 95% confidence interval) of cisapride and 57% (39-73%; 95% confidence interval) of cimetidine patients. After six weeks, both drugs significantly (P less than 0.01) decreased the intensity and frequency of heartburn, regurgitation, and the postural syndrome. No significant intergroup differences were found regarding endoscopic parameters or the improvement of heartburn and regurgitation. Concomitant antacid use was also comparable. Adverse effects were reported by four cisapride and nine cimetidine patients. These results indicate that the effects of cisapride compare well with those of cimetidine in terms of both esophageal mucosal healing and symptom relief.