Although the clinical manifestations and pathological physiology of hyperparathyroidism are now quite well recognized and understood, the diagnosis is still frequently overlooked until the opportunity for cure has been lost. This impression is borne out by the fact that when we recently surveyed the diagnostic files of seven general hospitals in a service area embracing about 1,500,000 persons over a 15-year period, only 11 proved cases of parathyroid adenoma were found. Nine of these cases are from hospitals with which we are directly connected, and only two were collected from other sources.Among the 11 cases 4 were discovered at autopsy and in 7 the clinical diagnosis was made during life and confirmed at operation. Only 1 of the 11 cases was recognized in connection with urinary calculus as the presenting symptom. In another case a nephrectomy had been done for a large ureteral stone with septic destruction of the