A series of 282 children subjected to pyloromyotomy for congenital hypertrophic pyloric stenosis seen in the years 1961--1980 is presented. The various features relating to presentation, diagnosis and treatment are compared and contrasted in those treated in the first decade, 1961--1970 (series A) with those treated in the second decade, 1971--1980 (series B). It is noteworthy that there was an increased demand for radiological investigation in the second decade, and the fact that the number of patients diagnosed by radiological means only has doubled (from 9% to 19%) in the two series is probably a reflection of medical training and attitude. There was a marked decrease in the amount of post-operative vomiting during the second decade of this study and there was a slight tendency to earlier discharge from hospital in the latter years. The series confirms that congenital hypertrophic pyloric stenosis treated by pyloromyotomy has no mortality and only a minimal morbidity.