BACKGROUND & AIMS: Treatment of necrotizing pancreatitis has become more conservative and less invasive, but there are few data from prospective studies to support the efficacy of this change. We performed a prospective, multicenter study of treatment outcomes among patients with necrotizing pancreatitis. METHODS: We collected data from 639 consecutive patients with necrotizing pancreatitis, from 2004 to 2008, treated at 21 Dutch hospitals. Data were analyzed for disease severity, interventions (radiological, endoscopic, surgical), and outcome. RESULTS: Overall mortality was 15% (n=93). Organ failure occurred in 240 patients (38%), with 35% mortality. Treatment was conservative in 397 patients (62%), with 7% mortality. An intervention was performed in 242 patients (38%), with 27% mortality; this included early emergency laparotomy in 32 patients (5%), with 78% mortality. Patients with longer times between admission and intervention had lower mortality: 0-14 days, 56%; 14-29 days, 26%; and >29 days, 15%,P <.001. Two-hundred eight patients (33%) received interventions for infected necrosis, with 19% mortality. Catheter drainage was most often performed as the first intervention (63% of cases), without additional necrosectomy in 35% of patients. Primary catheter drainage had fewer complications than primary necrosectomy (42% vs. 64%,P =.003). Patients with pancreatic parenchymal necrosis (n=324), compared to patients with only peripancreatic necrosis (n=315), had a higher risk of organ failure (50% vs. 24%,P <.001) and mortality (20% vs. 9%,P <.001). CONCLUSIONS: Approximately 62% of patients with necrotizing pancreatitis can be treated without an intervention and with low mortality. In patients with infected necrosis, delayed intervention and catheter drainage as first treatment improves outcome.