In an average 30 years of follow-up study, seven of 22 patients with primary adrenal insufficiency have had cardiac failure. Comparison of these seven with the 15 who remain free of this complication revealed that the former group were somewhat older and had higher incidences of unrelated cardiac disease and of nonsteroid-dependent hypertension, but that their replacement regimens, with respect to sodium supplementation and sodium-retaining steroids, were identical with the latter. Coincident with the appearance of cardiac failure, all seven patients had a decrease in sodium requirements. Adequate control of the adrenal disease was subsequently possible with elimination of mineralocorticoid support in one of the six who had initially required this therapy and a reduction in dosage in the other five. In all seven, dietary sodium supplements were no longer required. In three patients with severe failure, sodium restriction was imposed and diuretics were added, although the latter therapy has required close monitoring to avoid sodium depletion.