Between 1992 and 1999, 5 patients with chronic idiopathic myelofibrosis (MF) underwent splenectomy at our hospital. The median age at the time of splenectomy was 63 years (range, 58-69 years), while the median interval from diagnosis of MF to splenectomy was 38.2 months (range, 3.7-87.2 months). Reasons for splenectomy included symptomatic splenomegaly in 5 patients, transfusion-dependent anemia in 5, and refractory thrombocytopenia in 3. Although most of the patients with transfusion-dependent anemia and thrombocytopenia showed some improvement at 1 month after splenectomy, the response was durable in only 2 patients at 6 months. Post-surgical thrombocytosis of 1020 x 10(9)/l was observed in one patient. Blast cell counts in peripheral blood increased after splenectomy in 4 patients. Leukemic transformation occurred in one patient 5 months after splenectomy. Four patients eventually died (2 of infection, 1 of acute myelocytic leukemia, and one of heart failure). Overall median survival was 54.7 months (range, 10.9-110.0 months) and 10.2 months (range, 6.0-33.6 + months) from diagnosis and time of splenectomy, respectively. We confirmed the palliative role of splenectomy in advanced-stage MF, but sufficient consideration should be given to late complications including blastic transformation.