One of the significant complications of acute pancreatitis is pancreatic phlegmon, which is defined as "a solid mass of indurated pancreas and adjacent retroperitoneal tissue due to edema, infiltration by inflammatory cells and tissue necrosis." Pancreatic phlegmon can usually be resolved in a few weeks by nonsurgical conservative therapy. However, it is clinically important to differentiate pancreatic phlegmon from pseudocysts and abscesses, which do need surgical intervention. We recently experienced a pancreatic phlegmon patient, a 56-year-old alcoholic male, whose mass measured 24×16×22㎝ by CT and was resolved with conservative management.