Idiopathic thrombotic thrombocytopenic purpura (TTP) is a life-threatening disease mediated by autoantibodies directed against ADAMTS-13. A number of small series and case reports have shown promising results with rituximab in refractory or relapsed TTP. In this report, we present 13 patients with TTP treated with rituximab. Twelve of the 13 patients (92%) achieved complete response; no subsequent relapses occurred with median follow-up of 24 months (range, 13-84 months). The addition of rituximab to standard therapy appears to be effective in sustaining long-term remission in TTP. However, the optimal dosing and timing of rituximab warrant further investigation. Am. J. Hematol., 2009. (c) 2009 Wiley-Liss, Inc.