The occurrence of tetany as an infrequent postoperative complication following subtotal removal of the abnormal thyroid gland is well recognized (1) (2). McCullagh in 1932 (2), reported an incidence of tetany of 1.3 per cent in a series of 11,500 cases in which thyroidectomy was performed at the Cleveland Clinic.The anatomical proximity of the parathyroid glands to the thyroid, the similarity of the signs and symptoms of postoperative tetany to those of idiopathic hypoparathyroidism, and the specific effect of calcium therapy, offer strong evidence that tetany following thyroid surgery is due to removal of, or injury to, the parathyroid glands during operation. Means and Richardson (1) observed that the frequency of postoperative parathyroid tetany depends roughly upon the amount of thyroid tissue removed. Thus, tetany rarely occurs after unilateral thyroidectomy; and is less common after the subtotal removal of adenomatous goitre than after that of exophthalmic goitre (1).Blumgart and his associates (3) (4) (5) (6) have shown that in patients without thyroid disease, complete removal of the normal thyroid must be performed to assure a persistently subnormal basal metabolic rate. To accomplish complete ablation of the thyroid gland, the region of the parathyroid bodies must be deliberately invaded. It was feared, therefore, that intractable tetany might frequently follow this operation.The present communication is a report of our clinical observations, and studies of serum calcium and serum phosphorus in relation to parathyroid function following the total removal of the normal thyroid gland for the relief of intractable heart disease and other conditions.2 Studies of the