A 79-year-old patient with post-polycythaemic myelofibrosis presented with severe hypersplenism. After splenic artery catheterization, cytosine arabinoside was given intrasplenically from November 1999 to March 2000 for 5 d/month at 10 mg/m2 and increased each month by 10 mg/m2. It was then administered by continuous infusion until June 2000, starting at 20 mg/m2/d and tapering by 5 mg/m2 every 2 weeks to a final daily dose of 5 mg/m2/d. The drug was then stopped. The spleen had decreased to one third of the initial volume. Clinical conditions and haematological indices improved substantially. Intrasplenic therapy could be a new therapeutic tool for hypersplenism in chronic idiopathic and post-myeloproliferative myelofibrosis.