The effectiveness of urokinase in declotting central venous catheters was retrospectively assessed in a pediatric population of 63 patients ranging in age from 4 days to 22 years (mean, 6.4 years). Results of treatment from 103 episodes of catheter occlusion were evaluated. Urokinase was instilled into occluded single-lumen catheters and into each lumen of double-lumen catheters, as well as into occluded implanted ports. Patency was restored to 101 of 103 occluded catheters, with no side effects observed subsequent to clearance of the catheters with the urokinase infusion. Significant cost savings were seen using urokinase to restore patency as compared to the cost of replacing the catheter. These data clearly support the use of urokinase in a pediatric population as a safe and cost-effective alternative to catheter replacement in cases of thrombotic occlusion.