Thirty five severely mentally retarded children with significant gastro-esophageal reflux were submitted to surgical treatment. The age range was 2 months to 13 years. Characteristics and presenting symptoms were chronic vomiting (62%), merycism (43%), gastro-intestinal blood loss (37%), recurrent pneumonia (65%) and failure to thrive (57%). Barium esophagogram demonstrated free gastro-esophageal reflux in all patients with an associated hiatus hernia being noted in 3 cases. An upper gastro-intestinal endoscopy was performed in 24 children. Esophagitis of 2 or 3 degrees was present in 16 cases. A standard medical treatment was used in all patients during 1 month to 3 years. The patients were referred for surgery because they had no response to medical management or they had hiatus hernia or esophagitis type II or III. The operative procedure performed was Nissen fundoplication without gastrostomy. The mean duration of follow-up was 5 years (range 6 months to 12 years). We have not reviewed 5 patients. Several post-operative complications occurred: 4 pneumonia (2 deaths), 2 small bowel obstructions, 4 dumping syndrome and 1 death without etiology. Late complications were important too: 6 persistent reflux, 2 small bowel obstructions (2 deaths) and 2 peritonitis (2 deaths). Three patients died of their brain damage during the study period, 6 months to 8 years following their surgical procedure. The authors insist on: The frequency of gastro-esophageal reflux in retardates with a frequent merycism associated. The search for this reflux must be systematically done because it provokes some respiratory problems and a bad general status which distressed the child but also the family or the institution caring for the child.(ABSTRACT TRUNCATED AT 250 WORDS)