The incidence and severity of aortic, sclerosis in rabbits, using daily intraven. injn. epinephrine, 0.5 to 0.75 [mu]g. per kg., was increased by the simultaneous subcut. injn. of thyroxine, 0.25 mg. per kg. Desoxycorticosterone, on subcut. injn., 0.5 to 1.0 mg. per kg., decreased the sclerosis due to epinephrine alone but failed to influence the sclerosis due to combined epinephrine[long dash]thyroxine treatment.