Within a 3-year period we observed six children, aged 3 months to 4 years, with dumping syndrome (DS) following Nissen fundoplication. Five were neurologically normal and one was slightly mentally retarded. Symptoms included postprandial tachycardia, diaphoresis, lethargy, severe retching, meteorism or gas-bloat syndrome, watery diarrhea, refusal to eat with failure to thrive, and developmental delay. Results of an oral glucose tolerance test did not correlate with the severity of symptoms. In one child severe retching led to recurrent paraesophageal gastric herniation, necessitating two reoperations and a gastrostomy. A lack of meal stimulated pancreatic polypeptide release in this patient indicated vagal damage. Initially five of the six children needed continuous intragastric feeding until bolus application of a carbohydrate-modified diet was tolerated. We conclude that the diagnosis of DS is often delayed in spite of characteristic clinical signs. Intensive postoperative follow-up after antireflux surgery should be mandatory in children.