The authors studied the activity of blood serum amine oxidase in patients with atherosclerosis obliterans and endarteritis obliterans. It was found that amine oxidase activity exceeded the normal value. 2.6 times in patients with stage 1-2 atherosclerosis obliterans and was reduced by more than 12 times in patients with stage 3-4 of the disease. The activity of the enzyme was absent in patients with endarteritis obliterans, whatever the stage of limb ischemia. On the basis of the obtained facts, the authors voice a new opinion on the nature of hypercatecholaminemia in obliterative diseases and suggest a new trend in the treatment of chronic ischemia of the limbs-activation of the processes of catabolism of vasoconstrictive biogenic amines.