Of 136 institutionalized severely retarded children, 20 (15%) had recurrent vomiting. Of these 20, 15 had gastroesophageal reflux diagnosed by x-ray examination, acid reflux text, or both. Esophagitis was noted by endoscopy in ten of 14 patients with GER. Four patients were anemic and six had had one or more episodes of aspiration pneumonia in the 12 months prior to study. Reduced basal lower esophageal sphincter pressure was the most common manometric abnormality noted in the patients with GER. Responses of the LES to bethanechol and swallow were normal, as was the basal pressure of the upper esophageal sphincter. Abnormal propagation of esophageal peristalsis was seen in six patients, all of whom had moderate or severe esophagitis. When compared to the nonvomiting retarded patients, the GER patients had significantly lower mental age and higher incidence of scoliosis. Patients with GER who had basal LES pressure less than 10 mm Hg did not improve with medical management. Recurrent vomiting is a common and serious problem in severely retarded children, the organic cause of which can be demonstrated by the application of appropriate investigative techniques.