This chapter discusses the diagnosis, evaluation and management of acute pancreatitis. Historical features of pancreatitis include its characteristic abdominal pain, classically described as epigastric in location and radiating to the back. This is typically associated with nausea and vomiting. Multiple scoring systems have been developed to predict the severity of illness in acute pancreatitis, but none of them should replace regular reassessment of the patient's clinical condition. The most commonly used scoring system is the Ranson score. A frequently cited definition of pancreatitis is the presence of at least two of the following: upper abdominal pain; serum lipase at least 3 times greater than the upper limit of normal; and CT findings suggestive of acute pancreatitis. Laboratory findings in acute pancreatitis most importantly include elevated serum levels of lipase and amylase.