Only in 1969 reliable information about glucagon and its different forms was acquired. Some factors are already known to increase or diminish the production both of pancreatic glucagon (nesidioglucagon) and of enteroglucagon. There are various methods for their study. In the present report some results are dealt with that may be of clinical interest, and the possibility of measuring those two kinds of hormones is pointed out as a diagnostic help in reactive and functional hypoglycemic syndromes. Information about glucagon in clinical medicine, however, is still -- on the whole -- scarce and insufficient to throw light on its several physiological and physiopathological aspects.