During a 10-year period we operated on 816 children with a diagnosis of acute appendicitis. Of these, 36 (4.5%) were under 5 years of age. A retrospective analysis was made of these 36 cases to assess the natural history, management and outcome in these children. Abdominal pain was the commonest symptom but was not invariable, being present in only 32 of the 36 children while vomiting was present in 28 children. Localized tenderness in the right iliac fossa was present in 21 children and generalized in 10. In 5 children there was a delay in diagnosis in excess of 18 h. The overall perforation rate was 50% as assessed macroscopically and was inversely proportional to the child's age. There was no mortality and the wound sepsis rate was 16.6%. The low incidence of acute appendicitis in very young children means that it is often overlooked. A high index of suspicion may contribute to earlier diagnosis and thereby reduce morbidity.