Prophylactic antibiotics in acute nonperforated appendicitis have been used for preventing infection after appendectomy. However, duration of antibiotic administration for surgical prophylaxis in Korea has been noted to be longer than those recommended in other countries. The objective of this study was to identify appropriate duration of prophylactic antibiotics in acute nonperforated appendicitis by comparing two different antibiotic regimens for their wound infection rates. Eighty-four acute nonperforated appendicitis patients were enrolled in this prospective, randomized, open trial and were assigned to one of two antibiotic regimens: cefoxitin 1 g every 8 hours given intravenously for 24hours or cefoxitin 1 g every 8 hours given intravenously plus sisomicin 75 mg every 12 hours given jntramuscularly for 72 hours. First doses were given just prior to the induction of anesthesia. Postoperative wound infections were detected in $4.8\%$ of the 72-hour-treated group (n=42), whereas none occurred in the 24-hour-treated group (n=42). However, the difference in the rates of wound infections between two groups was not statistically significant. The most frequently isolated microorganism from appendiceal tissues was E coli. In conclusion, administration of cefoxitin alone for 24 hours is sufficient as surgical prophylaxis in nonperforated appendicitis.