To compare patients with acute necrotizing pancreatitis without any additional complications during their hospital stay (Group A) versus patients with Acute Necrotizing Pancreatitis with additional complications during their hospital stay (Group B). Data obtained from a pre-existing base from hospitalized patients with diagnosis of acute necrotizing pancreatitis in the specialized unit of "Unidad de Pancreatitis Aguda Grave del Hospital Nacional Edgardo Rebagliati Martins" between 2000 and 2010. Data included patients with diagnosis of acute necrotizing pancreatitis, of ages 18 and over. Data from 215 patients with acute necrotizing pancreatitis was included. Patients from Group A represented 32% (68) and from Group B 68% (147). Group A had a average of 39 hospitalized days and Group B had an average of 56 days (p=0.01). From Group A 22% had more than 50% of necrosis while 43% of Group B had this extension of necrosis (p <0.05, OR 3.4, IC (1.12-10)). Of the 14 deaths of the population, all part of Group B, 12 of them had more than 50% of necrosis. Not every patient classified as severe acute pancreatitis, based on the presence of necrosis, behave likewise. It is an extended necrosis, described as more than 50% of pancreatic necrosis, and not the presence itself which will determine additional complications during the course of disease and a greater mortality.