Since the epoch making discovery in 1925 by Mandl1in Vienna and in 1926 by Du Bois2in this country that osteitis fibrosa cystica is a manifestation of hyperparathyroidism, the medical profession has been quick to apply this knowledge, and the literature of the past few years contains numerous case reports and metabolic studies on this, the classic form of hyperparathyroidism. There have been, in addition, excellent summary articles on the subject.3Most of the cases of hyperparathyroidism so far in the literature have represented the classic form; i. e., osteitis fibrosa cystica. This type of the disease is rare and offers no diagnostic difficulties. It is one of our chief objects in the present paper, however, to point out that other forms of hyperparathyroidism are not rare pathologic curiosities but conditions that every practitioner will not infrequently meet. The diagnosis must be considered and ruled in