Acute pancreatitis usually is a benign disease. However it can sometimes be severe with a 5% mortality. CT is the imaging technique of choice and should be performed in all cases. When clinical symptoms and laboratory findings are typical, the role of CT is to detect complications. In those cases, CT is ideally performed 72 hours after the beginning of symptoms. In other cases, CT can be performed earlier. The main usefulness of CT is to detect complications: necrosis, fluid collections and vascular involvement. Non-invasive imaging techniques, including US, are poorly sensitive for diagnosis of biliary pancreatitis.