The blood of 3 patients was studied. In addition to the well recognized chemical changes in the blood, serum Na was markedly diminished, reaching levels as low as 108 m. eq./l. Severity of the symptoms of adrenal insufficiency roughly paralleled the decrease in Na. A patient in extremis made a striking recovery upon the administration of 12-15 gm,. of NaCl daily, by mouth and rectum. The improvement followed over 2 mos. was paralleled by a return to normal in serum Na. The patient was maintained on a normal diet, in addition to which she ate 7 gm. of salt daily.