Macroamylasemia is characterized by an elevated serum amylase activity. It results from the circulation of a macromolecular complex consisting of amylase molecule and a serum component, often an immunoglobulin. The present study presents marked elevation of serum amylase level in a 43-year-old male, who had been admitted to our hospital for slight abdomen ache for 4 months. After treatment following pancreatitis, the symptom did not improve. Abdominal CT did not find any typical malignancy. The amylase clearance : creatinine clearance (C-AM: C-CR) ratio is 0.001. Polyethylene glycol (PEG) precipitation assay shows that the PEG-precipitated amylase activity for this patient is 77%, whereas all six healthy controls are below 52%. Therefore, in this case, the elevated amylase levels may be a result of marcroamylasemia.