Some degree of gastroesophageal reflux is very common in infants and tends to reverse with time. Therefore, the indications for an antireflux operation are not well defined. Furthermore, the complication rate and the ability of the fundoplication to grow remain to be determined. To answer these questions, we reviewed the records of patients 6 months of age or younger who underwent a Nissen fundoplication with gastrostomy tube placement between 1979 and 1985. There were 45 patients (25 boys and 20 girls) with birth weights of 0.65 to 4.3 kg. The consequences of gastroesophageal reflux were more varied than in older children. Severe respiratory problems were common, including recurrent aspiration or bronchopulmonary dysplasia in 60% and frequent apneic and bradycardiac spells in 17%. Failure to gain weight was present in 20% and intractable vomiting in 2.0%. As expected, 78% of these patients had congenital anomalies or acquired problems which, in many cases, were important to the prognosis. The diagnosis was confirmed by barium swallow in all but one patient in whom gross reflux during feedings was present. Initially, medical management was tried for 3 to 4 weeks. In one patient, however, the severity of the respiratory problems precluded trial beyond 12 days. The recommendation for operation was based only on the severity of symptoms attributed to gastroesophageal reflux. All patients underwent Nissen fundoplication with gastrostomy tube placement at 2 weeks to 6 months of age and weighing 1.02 to 6.95 kg. The only surgical complication was one gastrostomy leak. Prematurity or preexisting anomalies led to a 20% incidence of late unrelated deaths between 2 weeks and 23 months postoperatively. Improvement in symptoms occurred in our survivors with follow-up of 5 to 72 months. We conclude: Significant gastroesophageal reflux in infancy most frequently produces respiratory problems that can be life threatening. Nissen fundoplication can be a safe and effective procedure in infants 6 months of age or younger. Fundoplication appears to have good growth potential, and no late complications or feeding problems have occurred. Consequently, surgical correction can be recommended for infants not responding to conservative medical therapy.