Acute pancreatitis represents a wide spectrum of inflammatory disease involving the pancreas, peripancreatic tissues, adjacent solid organs, gastrointestinal and biliary tract, and vascular system. The extent and severity of the inflammatory process determines the prognosis of the patient and the need for specific surgical, endoscopic, and radiologically-guided intervention. Computed tomography is the single best imaging test for evaluating patients with acute pancreatitis. It can accurately stage the inflammatory process and can identify associated complications that require careful observation or immediate intervention. It also is essential for guiding percutaneous catheter placement for treatment of infected and noninfected fluid collections.