In a prospective controlled study the effect of antibiotics as the only treatment in acute appendicitis was evaluated. Of 40 patients admitted with a duration of abdominal pain of less than 72 h, 20 received antibiotics intravenously for 2 days followed by oral treatment for 8 days and 20 considered as controls were randomized to surgery. All patients treated conservatively were discharged within 2 days, except one who required surgery after 12 h because of peritonitis secondary to perforated appendicitis. Seven patients were readmitted within 1 year as a result of recurrent appendicitis and underwent surgery, when appendicitis was confirmed. The diagnostic accuracy within the operated group was 85 per cent. One patient had perforated appendicitis at operation. Antibiotic treatment in patients with acute appendicitis was as effective as surgery. The patients had less pain and required less analgesia, but the recurrence rate was high.