An infant with cutaneous criteria for neurofibromatosis had hyperplasia of the intestinal myenteric plexus and a clinical presentation mimicking Hirschsprung's disease. Many of his phenotypic features are also found in multiple endocrine neoplasia type IIb, a condition in which hyperplasia of the myenteric plexus is common. This case illustrates the overlapping nature of neural crest-derived conditions and the variable presentation of megacolon (ganglionic or aganglionic) in infancy.