The relevance of the upper gastrointestinal motility-stimulating effects of cisapride for the treatment of excessive regurgitation and vomiting in infants was studied in 137 patients aged less than 1 year. They were treated with placebo or with cisapride, 0.1 to 0.2 mg/kg three times daily, for up to four weeks. In a dose-dependent fashion, cisapride significantly reduced the frequency and severity of regurgitation: after four weeks of treatment at 0.15 to 0.2 mg/kg, only about 20% of infants still had moderate or severe regurgitation, compared with about two thirds of those treated with placebo. Although only a few patients were followed up, the duration of treatment (four weeks) appeared to be long enough to minimize relapse. Side effects were limited to phenomena indicative of stimulated bowel motility.