Sixty-one consecutive patients undergoing splenectomy for chronic immune thrombocytopenia were retrospectively evaluated. Platelet response was considered as complete (CR) when platelet count rose to > 100 x 109/l, partial (PR) when 30-100 x 109/l or absent (NR) if otherwise. Follow-up (mean time 7.6 years) was possible in 54 patients. Forty-eight patients (88%) had an immediate response to splenectomy (39 CR, 9 PR) whereas six (12%) were NR. Thirty-six responders (67%) had sustained remission (31 CR; 5 PR) without further treatment; thrombocytopenia recurred in 12 patients (33%). The probability curve of continued remission showed a constant relapse-rate during the first 36 months; a further step of relapse was observed beginning 70 months after surgery. The only positive predictive factor for the long-term response to splenectomy was age < 40 (P < 0.005). Neither duration of thrombocytopenia nor previous response to medical treatment (steroids and/or intravenous immunoglobulins) were related to splenectomy response.