To determine the effect of timing of surgical intervention for necrotizing pancreatitis. Design: Retrospective study of 53 patients and a systematic review. Setting: A tertiary referral center. Main Outcome Measure: Mortality. Results: Median timing of the intervention was 28 days. Eighty-three percent of patients had infected necrosis and 55% had preoperative organ failure. The mortality rate was 36%. Sixteen patients were operated on within 14 days of initial admission, 11 patients from day 15 to 29, and 26 patients on day 30 or later. This latter group received preoperative antibiotics for a longer period (PϽ.001), and Candida species and antibiotic-resistant organisms were more often cultured from the pancreatic or peripancreatic necrosis in these patients (P=.02). The 30-day group also had the lowest mortality (8% vs 75% in the 1 to 14-days group and 45% in the 15 to 29days group, PϽ.001); this difference persisted when outcome was stratified for preoperative organ failure. During the second half of the study, necrosectomy was further postponed (43 vs 20 days, P = .06) and mortality decreased (22% vs 47%, P=.09). We also reviewed 11 studies with a total of 1136 patients. Median surgical patient volume was 8.3 patients per year (range, 5.3-15.6), median timing of surgical intervention was 26 days (range, 3-31), and median mortality was 25% (range, 6%-56%). We observed a significant correlation between timing of intervention and mortality (R=−0.603; 95% confidence interval, −2.10 to −0.02; P =.05). Conclusion: Postponing necrosectomy until 30 days after initial hospital admission is associated with decreased mortality, prolonged use of antibiotics, and increased incidence of Candida species and antibioticresistant organisms.