The safety and efficacy of a single daily dose of netilmicin plus metronidazole after appendicectomy for gangrenous and perforated appendicitis was compared with the traditional thrice daily dosage. Twenty patients were enrolled in each group. The antibiotics were given intramuscularly for seven days after operation. Eradication of infection was observed in all patients and the postoperative wound sepsis was the same for each group. A significantly higher peak serum netilmicin level was achieved in the group receiving a single daily dose but nephrotoxicity was not observed. We concluded that the single daily dose of netilmicin was well tolerated and was as efficacious in this small series as the thrice daily regimen. The single-dose regimen has the advantage of simplicity and potentially increased bactericidal activity.