Defibrination with the snake venom enzyme Arwin is one of the numerous possibilities for the therapy of peripheral arterial obstructive disease. The number of complications is relatively small. In 58 patients with peripheral arterial occlusive disease stages III to IVa treated with Arwin the success rate was 50--60%. The ultrasonic Doppler pressures in the arteries of the ankle can be helpful for indicating Arwin therapy. Complications were not observed in combined treatment with hemodilution, intraarterial injection or simultaneous administration of heparin.