Five cases of infantile pyloric stenosis, three associated with esophageal atresia and tracheoesophageal fistula, one with Hirschsprung's disease and one with exomphalos are described. The etiologic factors, especially the role of gastrostomy, in the apparently higher incidence of pyloric stenosis in babies with alimentary tract anomalies are discussed. The diagnosis of pyloric stenosis may be difficult in these circumstances because of the absence of, or difficulty in, eliciting the usual signs. Clinical signs often being inconclusive, radiologic studies must be performed in all suspected cases. Five cases of infantile pyloric stenosis, three associated with esophageal atresia and tracheoesophageal fistula, one with Hirschsprung's disease and one with exomphalos are described. The etiologic factors, especially the role of gastrostomy, in the apparently higher incidence of pyloric stenosis in babies with alimentary tract anomalies are discussed. The diagnosis of pyloric stenosis may be difficult in these circumstances because of the absence of, or difficulty in, eliciting the usual signs. Clinical signs often being inconclusive, radiologic studies must be performed in all suspected cases.