We report hyperamylasemia associated with normal serum lipase in a 47-year-old female patient with suspected diagnosis of acute pancreatitis. Besides the markedly decreased amylase clearance/creatinine clearance ratio (Cam/Ccr = 0.41 %), the polyethylene glycol (PEG) precipitating 87% of the amylase activity in the serum also indicates the presence of macroamylase moleculase and confirms the diagnosis of Type 1 macroamylasemia. Thus when a patient has upper abdominal pain with hyperamylasemia, normal serum lipase, both acute pancreatitis and macroamylasemia should be considered, and the check of Cam/Ccr ratio and PEG precipitation of amylase is first recommended.