PURPOSE: It is controversial to treat complicated appendicitis in pediatric patients on several points, especially optimal time for appendectomy. The purpose of this study is to determine optimal time for operation in perforated appendicitis in pediatric patients. METHODS: Children with perforated appendicitis under the age of 14 underwent appendectomy between January 2006 and December 2008 at Ewha Womans University Mokdong Hospital were analyzed retrospectively according to factors which may affect the postoperative hospital course such as complications, time of beginning of diet, and length of hospital stay. RESULTS: During the study period, 357 patients with acute appendicitis underwent appendectomy and 118 patients were diagnosed with perforated appendicitis. Comparing symptom durations between more than 48 hours and less, the former induced significantly higher postoperative complication rates. Body temperature above 37.5degrees C at admission affected significantly higher complication rates and delay of beginning of diet. Children with intraabdominal abscess at appendectomy showed higher complication rates than without abscess. Children who underwent operation in the daytime started diet significantly earlier and showed less complication than those operated on at night. The frequency of preoperative antibiotics administration did not alter the postoperative hospital course. CONCLUSION: For the children diagnosed with perforated appendicitis, non-urgent appendectomy in the daytime after initial conservative management including intravenous administration of antibiotics, hydration, and correction of serum electrolyte is safer and more efficient than performing emergency operation, and moreover there is no necessity for secondary admission for interval appendectomy.