The authors report a case of macroamylasemia in which the diagnosis was made with some difficulty. A hyperamylasemia was discovered after the patient, an alcoholic, had been hospitalized for atypical abdominal pain and weight loss, and this was thought to be due to an acute episode of chronic pancreatitis. The absence of an incrase in amylasuria suggested the presence of a macroamylasemia, and both diagnoses were confirmed by suitable exploratory investigations. Alcoholic cirrhosis was also present. The two main known types of macroamylase and their iatrogenic variant are described as well as the incidence of this biological anomaly in the general population. Confirming the presence of this anomaly in the plasma is a delicate and complex procedure. Simultaneous study of amylase-creatinine clearance ratio was thought to be a decisive test, but this does not appear to be true.