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Restriction of the sodium chloride intake as a therapeutic measure in hypertensive vascular disease was first advocated many years ago (1, 2, 3). Although subsequent investigators (4, 5, 6, 7) claimed that the addition or removal of salt from the diet failed to influence the blood pressure level significantly, interest in the subject has recently been renewed.Selye and his coworkers (8) noted a striking hypertensive effect when sodium chloride was administered to experimental animals receiving injections of desoxycorticosterone acetate. Grollman and his associates (9) observed that drastic reduction in sodium intake resulted in a decline in blood pressure in some hypertensive patients. They believed it probable that the beneficial effects of the diet proposed by Kempner (10) might be due to the restriction of salt. Recently evidence has been presented (11) that sodium chloride potentiates the pressor activity of desoxycorticosterone acetate when injected into rats rendered nephritic with nephrotoxic serum.The present study was undertaken to reexamine the relationship of sodium chloride to hypertensive vascular disease in man. METHODSMen and women with uncomplicated hypertensive vascular disease were studied on the wards of the Presby- urine concentration tests, and in all instances the venous pressure was within normal limits.Blood pressures were measured each morning in the same arm by the same observer, with the subject quiet and relaxed in bed, the head of which was raised to a 30°angle. At least 5 and usually 7 or 8 readings were taken at half-minute intervals and the lowest systolic and diastolic value recorded. This value was designated the "resting" blood pressure as compared to "casual" readings taken under various conditions of activity at other times during the day. In order to secure an adequate baseline, it was found obligatory to carry out preliminary observations for at least 3 weeks.All subjects were kept in bed until after blood studies and blood pressure measurements were made, and ambulatory activity was standardized at a constant level the rest of each day. The patients were weighed daily before breakfast on the same scales. The daily fluid intake and urine output were recorded, distilled water being supplied for drinking purposes.Throughout the study the patients were given a constant diet and fluid intake. Identical salt-poor daily menus were prepared. Repeated direct analyses of aliquots taken from an entire day's cooked diet gave values of between 0.25 to 0.35 grams of sodium or considerably less than 1 gram of sodium chloride per day. These salt-poor diets yielded 1,700 to 2,200 calories and 70 to 80 grams of protein, and did not include special ingredients such as dialyzed milk. Sodium chloride was administered by mouth using weighed salt shakers, additional supplements being given in some instances in the form of enteric-coated tablets. When indicated, desoxycorticosterone acetate (DCA) was injected subcutaneously in doses of 5 mgm. twice daily.The urine chloride was determined daily fr...