Salvage of a free-tissue transfer, when postoperative vascular compromise is detected, depends largely upon the restoration of a patent microcirculation. The therapeutic efficacy of thrombolytics infused directly into the failing flap has been clearly demonstrated. In this experiment, the authors investigated whether the method of selective administration of urokinase to failing skin flaps in 68 Sprague-Dawley rats had any effect on flap survival. In one group of animals, postischemic flaps were perfused with 100,000 IU of urokinase given by manual injection, and via a pressurized delivery system (150 mmHg) in the other group. Flap survival was assessed at 7 days. A significantly greater survival was seen in flaps treated with urokinase by controlled pressure infusion (p < 0.01). This simple method is suggested to increase the efficacy of urokinase used in the context of flap salvage.