Radiosynovectomy offers a potentially effective, minimally invasive option for patients with chronic hemarthrosis and synovitis. The long-term outcome of patients with hemophilia who were treated with phosphate-32 chromic phosphate radiosynovectomy was evaluated. One hundred twenty-five procedures in 81 patients were done. Two- to 10-year followup by age and joint included joint bleeding and quality-of-life assessment. In addition, a relative cost comparison, scintigraphic imaging, and evaluation of biodistribution of the radionuclide were done. Of 125 procedures, 54% resulted in complete cessation of bleeding into the treated joint after the procedure, and 73% of patients reported improved mobility of the treated joint. Of patients 18 years old and younger, 79% had a greater than 75% reduction in bleeding incidence, and of patients older than 40 years, only 56% had a similar reduction. Seventy-nine percent of patients surveyed had a significant improvement in quality of life attributable to the treated joint. No evidence of significant leakage was observed. Billing records analysis indicated that radiosynovectomy costs less than 5% of surgical synovectomy. Phosphate-32 chromic phosphate radiosynovectomy is a clinically useful, safe, and cost-effective outpatient procedure in the treatment of patients with chronic hemarthrosis and synovitis.