Male and female, 100 days old, spontaneously hypertensive rats (SHR) were divided into two major groups: intact and uninephrectomized, given either no treatment, 1p.100 saline drinking water, 1p.100 saline + Deoxycorticosterone (DOC), or DOC alone. The DOC (Percorten pivalate) was given subcutaneously 2 times weekly, at a dose level of 2 mg/rat for 8 weeks. At autopsy, the combination of DOC + saline caused: the greatest exacerbation of blood pressure, marked catabolism, adrenal hypertrophy and thymic involution, little increase in heart weight, but a marked increase in kidney weight, elevated triglyceride and free fatty acids, cerebral and myocardial necrosis, fibrinous hyalinization of the cerebral, coronary, mesenteric, renal, testicular and ovarian arteries, foci of aortic cartilaginous metaplasia, PAN, foci of hepatic necrosis, and extensive lipid depletion from the zonae glomerulosa. Circulating corticosterone levels were suppressed to below normal levels. Excursion of circulating CPK levels coincided with the finding of myocardial necrosis and cerebral damage. It is suggested that the genetically-mediated hypertension of SHR is programmed through abnormal activity of the hypothalamic-pituitary axis and the specific morphologic make-up of arterial lesions is dependent upon the variety of adrenal or gonadal steroids secreted and their conditioning effect on the arterial wall.