In this paper an analysis has been made of 145 cases of congenital hypertrophic stenosis of the pylorus which have been treated by operation at the Royal Edinburgh Hospital for Sick Children during the twelve-year period 1922 to 1933 inclusive. In every case a positive diagnosis of pyloric stenosis was confirmed at operation, and no doubtful cases-have been included in the series. Those treated by medical measures only, such as repeated gastric lavage, are not considered, although in a large proportion of the series treatment had been carried out in the medical wards prior to operation, with a view to improving the general condition of the patient. It is not proposed to discuss in detail the symptomatology of congenital pyloric stenosis, but merelyto analyse the results of treatment in this series of hospital cases. Sex and Age Incidence Out of the total of 145 cases 125 were males and twenty females, representing a preponderance of males over females of 6.25 to 1. The 1931 census figures for 35r wI '.3 VI I GRAI'H 1.-Showing age on admission and age at first symptom for the total cases.