To the Editor.— The report of the Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure is clear, concise, and timely (237:255,1977). There is an important point not mentioned in the article, however. This point is demonstrated in the article immediately following by Blum et al ("Reversible Hypertension Caused by Hypercalcemia of Hyperparathyroidism, Vitamin D Toxicity, and Calcium Infusion, 237:262, 1977). I personally have seen several such persons, including one patient with primary hyperparathyroidism and another with excessive ingestion of calcium carbonate. The latter patient had encephalopathy and blood pressure in the malignant range. These patients achieved normal blood pressure with control of the hypercalcemia. Therefore, in our program, we now insist on obtaining a serum calcium measurement prior to initiating antihypertensive therapy. This is not merely a diagnostic necessity. The usual initial therapy with thiazides will worsen hypercalcemia and produce more problems than benefits. Calcium measurements