Popliteal aneurysms may threaten the viability of lower limbs, especially in the case of occlusion and poor run-off. In case of acute ischemia, thrombolysis can be used before surgery to clear the tibial arteries and enhance the results of subsequent bypasses. The procedure starts with an arteriography to show the arterial tree, then a recanalization is attempted. By means of a microcatheter pushed into the thrombosis, Heparin (1000 Units/h) and Urokinase (4,000 Units/h) are injected in situ. Arteriograms are repeated in order to control the placement of the catheter. Anticoagulant and fibrinolytic doses are biologically surveyed. Local and general complications are rare with the new techniques of fibrinolysis. Hemorrhagic complications following surgery are low despite the previous fibrinolytic treatment. Better success rates of bypasses, performed to relieve acute ischemic complications of popliteal aneurysms, should be achieved with this new modality of treatment.