A complex case of macroamylasemia in an alcoholic subject with chronic pancreatitis is presented here. The existence of a macroamylase, suggested by hyperamylasemia associated with low amylasuria and by values of the ratio amylase clearance/creatinine clearance lower than 1%, was confirmed by the profile of the amylase activity after filtration on gel of the patient's serum. The macroamylase activity of samples taken at various times over a period of seven months presents a variable characteristic: lowered at the beginning of the fourth month, it rose suddenly following a portal systemic encephalopathy, then became nil a fortnight later. This oscillating character found during the following months is not associated with the values of the serum amylase. The subject's pancreatic juice had no macroamylasic activity but the pancreatic amylase, in vitro, may be feebly linked to a constituant of the patient's serum. The nature of the protein associated with the amylase was not discovered. To in vivo variations of the macroamylase activity may be added the notion of in vitro variability for a sample conserved at -18 degrees C.