1. Two cases of hypertrophic pyloric stenosis occurring in adults are presented. One case is of the congenital type. The second case was associated with a localized follicular gastritis. 2. The etiology of hypertrophic pyloric stenosis as it occurs in adults is discussed, and the possibility of causative factors in addition to simple spasm are mentioned. 3. The lack of absolute diagnostic criteria which would exclude other lesions, makes surgical operation and tissue examination necessary. 4. The condition is not rate in adults, and should be considered as a diagnostic possibility in pyloric obstruction.