PURPOSE: This study was aimed to evaluate the effect of time of surgery for acute appendicitis on surgical outcomes to optimize the timing of appendectomies. METHODS: Medical records of patients who underwent an appendectomy were reviewed to obtain data on time of symptom onset, time of hospital presentation, and start times of surgery. Surgical findings were used to define appendicitis as either uncomplicated or complicated. The uncomplicated group included patients with simple, focal, or suppurative appendicitis, and the complicated group included patients with gangrenous, perforated appendicitis or periappendiceal abscess formation. The 2 groups were analyzed by age, sex, and time. RESULTS: A total of 192 patients were analyzed. The mean time from symptom onset to start of operation showed a significant difference between both groups (1,652.9 minutes vs. 3,383.8 minutes, P < 0.001). The mean time from hospital visit to start of operation showed no difference between both groups (398.7 minutes vs. 402.0 minutes, P = 0.895). Operating within 24 hours of symptom onset had a relative risk of 1.738 (95% confidence interval, 1.319-2.425) for complications. Operating more than 36 hours after symptom onset was associated with an increased risk of postoperative ileus and a longer hospital stay. CONCLUSION: Complicated appendicitis is associated with a delay in surgery from symptom onset rather than a delay at hospital arrival. Surgeons should take into account the time from symptom onset when deciding on the timing of appendectomy. We recommend that appendectomy be performed within 36 hours from symptom onset.