Abstract： Background Femoral artery thrombosis is one of the most common complications of catheterizations in infants and young children. This study was conducted to investigate the feasibility and effectiveness of thrombolytic therapy for femoral artery thrombosis after left cardiac catheterization in children.Methods Thrombolytic therapy with urokinase was carried out in children with femoral artery thrombosis after left cardiac catheterization. Each patient was given a bolus injection of heparin (100 U/kg). A bolus of urokinase (30 000-100 000 U) was injected intravenously, and then a continuous infusion of 10 000-50 000 U/h was administered. Transcatheter thrombolysis was performed once previous procedures failed.Results Eight patients (aged (3.1±2.3) years (8 months to 7 years), body weight (13.1±4.2) kg (7 to 20 kg)) presented lower limbs ischemia alter left cardiac catheterizations was performed. Seven patients accepted thrombolytic therapy with urokinase. In 5 patients, peripheral intravenous thrombolysis was successful with restoration of a normal pulse. In the other 3 cases, peripheral intravenous thrombolysis failed, followed by successful transcatheter thrombolysis. The average duration of therapy was (7.25±5.31) hours (1-17 hours). The average doses of heparin and urokinase were (1600±723) U (800-3000 U) and (268 571±177 240) U (50 000-500 000 U), respectively. There were no statistically significant differences in partial thromboplastin time before and during urokinase therapy ((40.6±22.3) to (49.9±39.2) seconds). However, the prothrombin time was significantly longer ((12.7±9.58) to (48.1±18.6) seconds, P<0.05). Patency of the target vessel was evaluated in all the patients for 2 weeks and no occlusion recurred.Conclusion Thrombolytic therapy with urokinase is a safe and useful modality in children with femoral artery thrombosis after left cardiac catheterization.