摘要It is widely believed that infection of pancreatic necrosis is a late event in the natural course of acute pancreatitis. This paper discusses the available data on the timing of pancreatic infection. It appears that infected pancreatic necrosis occurs early in almost a quarter of patients. This has practical implications for the type, timing and duration of preventive strategies used in these patients. There are also mplications for the classification of severity in patients with acute pancreatitis. Given that the main determinants of severity are both local and systemic complications and that they can occur both early and late in the course of acute pancreatitis, the classification of severity should be based on their presence or absence rather than on when they occur. To do otherwise, and in particular overlook early infected pancreatic necrosis, may lead to a misclassification error and fallacies of clinical studies in patients with acute pancreatitis.