From 1946 to 1977, 228 infants were operated on for congenital hypertrophic pyloric stenosis in the Tel-Aviv Municipal Medical Center, all by the method of Fredet-Ramstedt. An evaluation was made of the late morbidity in 41 patients, ranging in age from 15 to 30 years. The emphasis is on gastrointestinal diseases and their possible connection to the operation. Twenty-four of 41 patients had gastrointestinal symptoms, including dyspepsia, diarrhea, constipation, and abdominal pains. X-ray examination of the stomach was performed in 31 patients, in order to examine the structure and function of the stomach. Five patients showed clear signs of ulcer disease, four in the duodenum and one in the stomach. Another five patients showed mild deformation of the duodenal bulb, and two showed signs of gastritis. No correlation was found between the severity of the congenital pyloric stenosis and the presence of later illness or disturbances.