Congenital hypertrophic pyloric stenosis has been written about frequently and its treatment has become moderately well standardized; nevertheless, in the series of over a thousand cases that have occurred in the Children's Hospital, situations have arisen which either are not emphasized in the literature or are in need of clarification. It should be noted that this report deals with patients operated on by various members of the surgical visiting and resident staff. The mortality of this disease in any children's hospital should not rise above 1 or 2 per cent. To attain such a result requires attention to the details of preoperative and postoperative care as well as to the operative technic. One should also be on the alert for complications or the occasional associated anomalies. In 1939 Ladd and Gross1reported a series of 765 cases of pyloric stenosis treated in this hospital. In 1933 Lanman and Mahoney