Thirty-five complete arterial occlusions of pelvis and extremity in 29 patients were treated with intraarterial urokinase infusion therapy. In 28 limbs, the occlusions were due to arteriosclerotic change and in 7 lesions, the occlusions were due to Burger's disease. The patients with arteriosclerotic change ranged in age from 52 to 84 years with a mean age of 68 years, and the patients with Burger's disease ranged in age from 35 to 47 years with a mean age of 43 years. There were 24 men and 5 women. The estimated duration of the occlusion was from 5 days to 5 years with a mean duration of 11 months. The length of the occluded segments ranged from 1 to 45 cm with a mean length of 13.9 cm. The occlusion was located in the iliac artery in 13 patients, the femoral artery in 11 patients, both the iliac and the femoral artery in 2 patients, the popliteal artery in 5 patients, the femoro-popliteal artery in 1 patient, the brachial artery in 2 patients and the radial artery in 1 patient. The infusion catheter was gently advanced into the proximal portion of the clot over a flexible guide wire, and urokinase was infused at a rate of 5000-10000 IU/min, as a short term high dose infusion (SHI), until antegrade blood flow was reestablished. The catheter was then withdrawn to a point proximal to all of the remaining clot, and the infusion rate was reduced to 10000-20000 IU/h as a continuous low dose infusion (CLI). After thrombolytic recanalization, a percutaneous transluminal angioplasty (PTA) was performed in those cases which demonstrated a residual narrowing of the lumen. The initial success rate was 86%. Reocclusions were observed in 5 lesions (17%) and a second recanalization was successful in 2 of 3 patients. The 1-year cumulative patency rate following recanalization was 88.4% and the 2-year patency rate was 78.6%. No significant complications directly related to the procedure were observed. SHI combined with CLI and PTA appears to be an effective and safe therapy for chronic long segmental arterial occlusion.