To determine if there has been a genuine fall in the incidence of acute appendicitis, an epidemiological study using HAA and Korner datasets for the years 1975-1994 was carried out to identify those children and young adults undergoing appendicectomy for acute appendicitis. The overall incidence of acute appendicitis fell from 1.84/1000 to 1.17/1000. This fall was statistically significant (R2 = 0.74, P < 0.01). The decrease was significant in both males (overall reduction, 34%) and females (overall reduction, 40%). No significant reduction was observed in either males or females between 15 and 19 years of age. The overall reduction remains essentially unexplained, but may have implications for health planning and provision of services.