To evaluate the efficacy, safety, and primary patency of percutaneous mechanical declotting of thrombosed dialysis grafts using latex balloons. Fifty-nine patients with 86 episodes of dialysis graft thrombosis underwent percutaneous mechanical declotting with balloons using crossing catheter or transjugular technique. Vital signs, peripheral oxygenation, technical success, procedure time, and complications were recorded prospectively. Technical success was defined as a patent graft at the completion of the procedure. Clinical success, defined as successful dialysis for 1 week, and primary patency were obtained retrospectively from review of the dialysis records. Technical success was achieved in 74 of 86 procedures (86%). Median procedure time was 115 minutes, including failed cases. Ten of the 12 technical failures were due to resistant vascular stenoses precluding graft patency, despite removal of thrombus. There were no immediate complications. One patient died of sepsis 4 days after declotting. Clinical success was achieved after 65 of 86 procedures (76%); nine grafts thrombosed within 1 week of a technically successful declotting procedure. Primary patency (including technical failures) was 37% at 3 months, 31% at 6 months, and 17% at 12 months. Mechanical declotting is an effective means of restoring patency to thrombosed dialysis grafts.