Splenectomy is the only treatment of ITP known to have “curative” effects in a substantial fraction of patients. However, the true long-term outcome is uncertain and controversial because published series have not adjusted for the duration of follow-up. This IRB-approved retrospective study included all patients with ITP who underwent splenectomy between 1988-1993 at three major medical centers and required a minimum postoperative 5-year follow-up. Complete response (CR) was defined as all postsplenectomy platelet counts >150 × 109/L without treatment; partial response (PR) as platelet counts ≥50 × 109/L without treatment; and failure as platelet counts <50 × 109/L or receiving therapy after splenectomy. Seventy-five patients identified with ITP underwent splenectomy from 1988 to 1993. Three patients died prior to 5-year follow-up, and 56 of the 72 patients (78%) were evaluable with follow-up for five years or longer, median 7.5 years. The immediate postoperative complete remission rate was 77%; 57% of patients have remained in prolonged CR. Thirty-seven patients (66%) have not required any therapy after splenectomy. Eight patients had platelet counts >150 × 109/L for 4–8.5 years before relapsing; no clear plateau was attained in the remission curve. There was no operative mortality. Ten patients (18%) reported minor postoperative bleeding episodes. No life-threatening infections, significant heart disease, or pulmonary hypertension developed after splenectomy in the 434 patient-years of follow-up. This study helps to define the long-term results of splenectomy for ITP. Am. J. Hematol. 72:94–98, 2003. © 2003 Wiley-Liss, Inc.