Although the etiologies of Hirschsprung's disease and infantile hypertrophic pyloric stenosis remain unclear, it is certain that in Hirschsprung's disease, there is an absence of myenteric ganglia. In pyloric stenosis, there is a decreased number of ganglia, but this may be secondary phenomenon. The occurrence of both Hirschsprung's disease and pyloric stenosis in any single patient is uncommon, disputing a common etiology on statistical grounds. The authors have recently seen two infants with both diseases, and have reviewed the histology and pathophysiology analyzing the possibility of a single cause.