Background: Although prophylatic antibiotics has been proven to be effective in reducing wound complications after appendectomy, the most efficacous dosage remains uncertain.Aim:To determine the optimal duration of antibiotics after appendectomy for non‐perforated acute appendicitis.Methods: From July 1995 to December 2000, all patients aged between 15 and 70 years with appendectomy performed via a right lower abdominal incision were considered for the study. Exclusion criteria included pre‐admission antibiotics, diabetes mellitus, known drug allergy and ruptured appendicitis. Intravenous Cefuroxime, 1.5g, and Metronidazole, 500 mg were given at induction of anaesthesia. After appendectomy, patients were randomized to one of the three treatment protocols: (A) no further antibiotics, (B) 2 more doses of antibiotics, or (C) a 5‐day course of antibiotics. Outcomes of surgery were compared using 1‐way ANOVA or Chi‐square where appropriate.Results: Of 275 patients recruited, 6 had normal appendix revealed by histology and were excluded. Treatment A, B and C were assigned to 92, 94 and 83 patients, respectively. The 3 groups were comparable in demographics and pre‐operative characteristics. The outcomes were as follows: Conclusions: A single dose of preoperative antibiotics is adequate for prevention of wound infection in non‐perforated appendicitis. Prolonged use of antibiotics is cost‐ineffective and may lead to unnecessary complications.