The 408 patients with symptomatic and endoscopic evidence of reflux esophagitis were enrolled in a double-blind, multi-center study. For 6 weeks, 201 patients (median age, 51 years; 59 women) were randomly assigned to receive 75 mg of roxatidine acetate twice daily and 207 (median age, 51 years; 62 women) received 150 mg of ranitidine twice daily. Baseline and final endoscopic findings were available for 158 of the roxatidine group and 156 of the ranitidine group who completed the study. After treatment, completely healed or residual erythema of the mucosa (conventional healing rate) was found in 68% of the roxatidine group and in 69% of the ranitidine group, complete healing of the mucosa, in 32% and 38%, and improvement in 83% and 84%. According to a reflux symptom index, at 6 weeks, 28% of 161 evaluable roxatidine-treated patients and 36% of 158 evaluable ranitidine-treated patients were asymptomatic during both the day and night. The conventional healing rates in this study were similar to those in nine previous studies of ranitidine; 3 roxatidine-treated patients and 4 ranitidine-treated patients dropped out of the study because of side effects. It is concluded that 75 mg of roxatidine acetate twice daily is as safe and effective as 150 mg of ranitidine twice daily in the treatment of reflux esophagitis.