OBJECTIVE To evaluate the safety and efficacy of cisapride in patients with gastroesophageal reflux disease. METHODS Patients (N = 177) were randomized to double-blind treatment with cisapride (10 or 20 mg q.i.d.) or placebo for 12 wk. Efficacy was determined by pre- and poststudy endoscopies, symptom assessments by patient and physician, and Maalox consumption. Safety evaluations included vital signs, electrocardiograms, clinical laboratory tests, and reports of adverse events. RESULTS Cisapride 10 mg significantly reduced daytime and nighttime heartburn at 4 wk compared with placebo. Cisapride 20 mg reduced both daytime and nighttime heartburn at 4, 8, and 12 wk, compared with placebo, and was also significantly superior to the 10-mg dose at 12 wk. The percent of patients with endoscopic healing was significantly higher with cisapride 20 mg than with placebo [healing: 51 vs 36% (p < or = 0.044)]. Maalox usage declined significantly with cisapride 20 mg compared with placebo. No clinically significant changes in safety variables occurred with cisapride. The most frequently reported adverse events in the cisapride group were diarrhea, headache, and sinusitis. CONCLUSIONS Cisapride 10 and 20 mg q.i.d. were safe and well tolerated in a population of patients with mild-to-moderate gastroesophageal reflux disease. Both symptoms and endoscopic grade improved after 12 wk of treatment with cisapride 20 mg q.i.d.