PURPOSE: During the night time decision making on patients suspicious of appendicitis is often difficult because diagnosis and timing for operation are frequently delayed. Therefore, we analyzed above cases and solution is suggested. METHODS: This retrospective study included 360 patients who underwent laparotomies for suspected appendicitis at Hanil Hospital during one year, from March 1998 to Feb. 1999. They were divided into two groups according to presenting time to physician (Day time: 6 a.m. to 6 p.m., Night time: 6 p.m. to 6 a.m.). Sex & age distribution, time of presentation to physician, duration of symptoms, symptoms & physical findings, white blood cell counts, interval from presentation to operation, hospital stay, and pathologic diagnosis were compared. RESULTS: There were no significant differences in sex & age distribution, duration of symptoms, symptoms & physical findings, white blood cell counts, pathologic diagnosis between the two groups. However, during the night time, the interval from presentation to operation was longer than that of the day time (9.15 hours versus 4.83 hours, p<0.001), the rate of delayed appendectomy during the night was 58.0%, the rate of negative laparotomy increased when appendectomy was delayed for more than 12 hours compared with less than 12 hours (28.1% vs 11.7%, p<0.01), and in the cases with perforated appendicitis, delayed appendectomy for more than 12 hours had longer hospital stay compared with less than 12 hours (12 days vs 9.44 days, p<0.01). Factors causing delayed appendectomy were related to the physician (42.5%), lack of anesthetic & nursing supports (19.5%), failure to structure the operation team (20.7%), and patient itself (17.3%). When white blood cell counts were rechecked in the next morning, levels above 10,000 cells/mm3 were highly associated with appendicitis in contrast to that below 10,000 cells/mm3 (91.7% vs 43.5%, p<0.002).