OBJECTIVE: The objective of this study was to compare the efficacy and safety of the proton pump inhibitor rabeprazole to that of the histamine-2 (H2)-receptor antagonist ranitidine in the treatment of erosive gastroesophageal reflux disease. The primary indicator of efficacy was the absence of esophageal erosions or ulcerations as determined by posttreatment endoscopy. Secondary indicators of efficacy included improvement in frequency and severity of daytime and nighttime heartburn. METHODS: A total of 338 patients were enrolled and randomly assigned to therapy with rabeprazole 20 mg once daily in the morning or to ranitidine 150 mg four times daily. At baseline and at 4 wk, patients underwent endoscopy for evaluation of esophageal lesions. Patients whose lesions healed by wk 4 had therapy discontinued; others remained on therapy and had repeat endoscopy at 8 wk. Also recorded at study visits were patients' ratings of heartburn symptoms and overall sense of well being, patients' reports of time lost from daily activities, antacid use, and adverse events. Serum gastrin levels were measured and argyrophil enterochromaffin-like cell histology evaluated at baseline and when the patient ended therapy. RESULTS: At wk 4, healing was observed in 59% (98/167) of patients assigned to rabeprazole therapy, compared with 36% (60/169) of those receiving ranitidine (p < 0.001). By 8 wk, healing was seen in 87% (146/167) and 66% (112/169) of patients in the rabeprazole and ranitidine groups, respectively (p < 0.001). There were also significant differences between the two groups favoring rabeprazole with respect to resolution or improvement of heartburn symptoms and improvement in sense of well-being. No drug-related serious adverse events were seen with either therapy; fewer patients assigned to rabeprazole had treatment-emergent signs and symptoms. Serum gastrin levels increased over baseline in the rabeprazole group, but the mean value remained within normal limits. CONCLUSIONS: Rabeprazole was superior to ranitidine in esophageal healing and symptom relief in patients with erosive gastroesophageal reflux disease, and was equally well tolerated.