Six small-breed, middle-age dogs with a history of chronic intermittent vomiting had benign pyloric lesions causing gastric outlet obstruction. Marked similarities were found in clinical signs, pathologic changes, and treatment results. The condition was classified as a syndrome and was named chronic hypertrophic pyloric gastropathy. The appearance of the obstructive lesions at surgery were various forms of mucosal hypertrophy. Microscopically, the syndrome was characterized by mucosal foveolar and glandular hyperplasia, cystic glandular dilatation, superficial mucosal ulcerations, and various cellular infiltrates. The affected dogs were successfully treated by surgical correction of the gastric outlet obstruction.