Congenital atresias of the pylorus or stomach are rare compared with complete obstructions elsewhere in the intestinal tract. A thorough review of the literature revealed seven previously reported case histories of patients in whom this diagnosis was made clinically or at autopsy. We have successfully treated two premature infants with prepyloric gastric mucosal atresia at Children's Hospital of Michigan. We would like to add their histories, along with a summary of our review, to the literature. Types of Obstruction and Review of the Literature Pyloric and gastric obstruction of the newborn can be divided into two general groups: complete and incomplete. The latter condition is common owing to the incidence of pyloric stenosis, which does not usually cause symptoms until the patient is 2 or more weeks of age. Another type of incomplete occlusion of the gastric canal is the result of obstruction by an intrinsic mass of the gastric