Objective: To examine the effect of delay from surgical admission to induction of anesthesia on outcomes after appendectomy for acute appendicitis in adults. Design: Retrospective cohort study with the principal exposure being time to operation. Regression models yielded probabilities of outcomes adjusted for patient and operative risk factors. Setting: Data were submitted to the American College of Surgeons National Surgical Quality Improvement Program database from January 1, 2005, through December 31, 2008. Patients: Patients with acute appendicitis who underwent an appendectomy. Main Outcome Measures: Thirty-day overall morbidity and serious morbidity/mortality. Results: Of 32 782 patients, 24 647 (75.2%) underwent operations within 6 hours of surgical admission, 4934 (15.1%) underwent operations more than 6 through 12 hours, and 3201 (9.8%) underwent operations more than 12 hours after surgical admission. Differences in operative duration (51, 50, and 55 minutes, respectively; P < .001) were statistically significant but not clinically meaningful. The length of postoperative stay (2.2 days for the >12-hour group vs 1.8 days for the remaining groups; P < .001) was statistically significant but not clinically meaningful. No significant differences were found in adjusted overall morbidity (5.5%, 5.4%, and 6.1%, respectively; P = .33) or serious morbidity/mortality (3.0%, 3.6%, and 3.0%, respectively; P = .17). Duration from surgical admission to induction of anesthesia was not predictive in regression models for overall morbidity or serious morbidity/mortality. Conclusions: In this retrospective study, delay of appendectomy for acute appendicitis in adults does not appear to adversely affect 30-day outcomes. This information can guide the use of potentially limited operative and professional resources allocated for emergency care.