NORRIS,1 in 1947, reported on 336 cases of parathyroid adenoma which he had been able to collect from the literature between 1903 and 1947. He suggested that during the subsequent 10 years all cases of parathyroid adenoma warranted publication. With this in mind, we are presenting a summary of all the cases of primary hyperparathyroidism that have been seen at the Lahey Clinic since the first case was diagnosed in 1933; eight of these cases have been reported previously.2 No attempt will be made to review the history of the knowledge of parathyroid diseases or the extensive literature on parathyroid physiology. The history of hyperparathyroidism has been reviewed in an interesting fashion by Albright,3 and the pathophysiology has been discussed in detail by Albright and Reifenstein.4 Although there is some diversity of opinion concerning the basic mechanism through which the parathyroid hormone acts, the ultimate effect of an excess of