From November 1, 1995, to April 30, 1997, in our outpatient dialysis facility, 7,179 or 24.3% of hemodialyses were performed with soft, cuffed, intravenous catheters as blood accesses. Inadequate blood flow (pump speed < 400 mL/min) was noted in 286 instances (4.0%). Locking of catheter lumina with 5,000 to 9,000 IU urokinase was only partly successful in three of 21 cases. Infusions of 20,000 to 40,000 IU urokinase in 25 instances during dialysis restored catheter function in 10 cases. In nine instances in which blood could not be aspirated from the catheter and dialysis could not be performed, the infusion was done through the catheter while the patient remained in the chair. In eight instances, the catheter was opened, and dialysis was performed on the next shift. In 162 instances, a new method was used to open failing catheters most conveniently, efficiently, and with minimal cost. Whenever a nonpositional deterioration of blood flow was noted, 250,000 IU urokinase was infused during dialysis over 3 hours, if there were no contraindications. Full restoration of pump speed was achieved during 132 infusions; in another 21 cases, blood flow improved. In 59 cases, in which an adequate pump speed was not achieved during the next dialysis, the infusion was repeated with restoration of blood flow in 50 instances and flow improvement in six; infusion was re-repeated in the nine instances without complete restoration of flow and in one of the 50 in which restoration of flow was temporary. Adequate flow was restored in nine of these 10 cases in which re-repeated infusion was done. Routine doses of heparin were used concomitantly with urokinase in all cases. No adverse reaction to urokinase has been encountered in any case. To maintain long-term catheter patency, warfarin therapy was started in patients who required repeated urokinase infusions. Vials of 250,000 IU, 9,000 IU, and 5,000 IU urokinase cost $358.47, $77.07, and $43.76, respectively. The higher cost of high-dose intradialytic urokinase as compared with the catheter "lock" is offset by the high probability of positive results, saving of nursing and patient time, and saving on transportation expenses. The convenience and cost are even more remarkably in favor of intradialytic urokinase compared with catheter stripping ($2,433) or surgical replacement ($3,060).