A randomized controlled trial in 374 patients requiring emergency appendicectomy to determine the value of topical ampicillin and an antiseptic solution of chlorhexidine and cetyl trimethyl ammonium bromide (Savlon) in preventing wound infection is reported. The application of 1 g of ampicillin powder to the wound significantly reduced wound infection in perforated appendicitis, but not in unperforated appendicitis. Wound irrigation with 1% cetyl trimethyl ammonium bromide was ineffective in preventing wound infection in all grades of appendicitis. When wound contamination is difficult to avoid, as in perforated appendicitis, topical ampicillin should be used to reduce the rate of wound infection.