Imaging of patients with acute pancreatitis requires an understanding of the subtypes and complications that were defined at the Atlanta symposium in 1992. In the last decade, several new entities have been recognized with important clinical implications. In this article, the radiological aspects of the terminology and classification of acute pancreatitis are reviewed and new entities are clarified. The roles of ultrasound, computed tomography, and magnetic resonance imaging in the diagnosis and evaluation of acute pancreatitis and its complications are discussed and the limitations of each imaging technique, when interpreting pancreatic and peripancreatic inflammatory disease, are addressed.