In this radiology lecture, we discuss the imaging appearance of necrotizing pancreatitis on both CT and MRI. Key points include: * According to the revised Atlanta classification, there are two types of acute pancreatitis: Interstitial edematous pancreatitis (IEP) and necrotizing pancreatitis (NP). * For IEP, fluid collection in first 4 weeks = acute peripancreatic fluid collection, after 4 weeks = pseudocyst. * For NP, fluid collection in first 4 weeks = acute necrotic collection, after 4 weeks = walled-off necrosis. * Non-enhancing hypoattenuating areas = necrotizing pancreatitis. * Gas suspicious for infection/emphysematous pancreatitis. * Vascular complications are important to identify. * Venous thrombosis: splenic, portal, and mesenteric veins. * Pseudoaneurysms: Splenic and gastroduodenal artery.