Gastric outlet obstruction in infants and children may be due to a partial, prepyloric antral diaphragm. Twelve new patients are added to the 32 described previously. Onset of symptoms varied from shortly after birth to five years. Nonbilious vomiting was the most common presenting symptom. Radiographic evaluation requires specific technique for demonstration of the web and to differentiate this from pylorospasm and pyloric stenosis. Gastroscopy was employed in three patients. Repair usually consisted of incision of the web and construction of a patulous gastric outlet. All patients remained asymptomatic after operation. The etiology of the webs remains unknown, but they may result from an excessive local endodermal proliferation early in gastric development.