Fifty-four children with proven infantile hypertrophic pyloric stenosis (IHPS) were treated by Ramstedt's pyloromyotomy during a 14-year period. Between the years 1986 and 1989 the mean incidence of the disease was noted to have risen by 2.72 per 1000 live births over the preceding 10 years. Statistical analysis confirmed a significant upward trend between the years 1976 and 1989. Analysis of the majority of the cases revealed comparable perioperative morbidity rates with other UK district general hospitals. There was no operative mortality. The character of IHPS in military personnel overseas has more in common with UK than international trends. The incidence in this subgroup may be rising.