To evaluate the safety and efficacy of the Castañeda brush catheter in the treatment of thrombosed hemodialysis fistulas and grafts. Twenty-six revascularization procedures with the Castañeda brush catheter combined with urokinase were retrospectively analyzed in 21 patients (mean age, 69 years; range, 35-87 y). Hemodialysis shunts were native arteriovenous (AV) fistulas (n=15; 16 procedures) or polytetrafluoroethylene grafts (n=6; 10 procedures). Major outcomes included procedure time, anatomic and clinical success rates, complication rate, and primary, primary assisted, and secondary patency. In 26 procedures, the brush catheter was used in combination with a mean dose of 239,792 IU urokinase (range, 60,000-300,000 IU). Additional angioplasty was performed in all procedures; five procedures (19%) required additional stent implantation. Mean procedure time was 99.2 minutes (range, 49-261 min). Anatomic and clinical success rates were 100% and 96.2%, respectively. Two minor complications (8%) occurred, neither of which was device-related: one case of extravasation treated by balloon tamponade and one hematoma at the distal puncture site without the need for surgery or transfusion. Primary patency rates were 87%, 62%, and 50% at 3, 6, and 12 months, respectively, for AV fistulas, and 50%, 33%, and 17%, respectively, for grafts. Assisted primary patency rates were 93%, 77%, and 70% at 3, 6, and 12 months, respectively, for AV fistulas, and 50%, 33%, and 17%, respectively, for grafts. At 3, 6, and 12 months, secondary patency rates were 93%, 85%, and 80%, respectively, for AV fistulas, and 83%, 67%, and 50%, respectively, for grafts. The Castañeda brush catheter is a safe and effective pharmacomechanical thrombectomy device for the treatment of thrombosed hemodialysis grafts and native fistulas.