Malmö General Hospital is the single referral unit for 240000 people living in Malmö, Sweden. In order to assess the influence of age on annual risk and clinical course in acute appendicitis we reviewed hospital records of 673 randomly selected patients operated on 1972-1978. Annual incidence in 20-year-olds 4/1000 was four times higher than in the 59-70-year-olds. Perforation was more common in old than in young patients. Fifty-four percent of all cases above 60 were perforated. Patients older than 60 with perforation had the longest duration of symptoms. Age above 60 and perforation were both associated with an increased body temperature at arrival an increased risk of wound infection and other complications and a longer period of hospitalization.