Abstract:In 12 patients having myelofibrosis with myeloid metaplasia (MMM), recombinant‐ α interferon (r‐αINF) was given for 16 weeks at an initial dose of 3 times 106U/day as a cytoreductive agent. At the end of the 16th wk, Hb showed minor changes; WBC were reduced from 43 times 109/l, range 6.4–69.4, to 16 times 109/l, range 5–39 (p = 0.05); platelets decreased from 845 times 109/l, range 215–1748, to 370 times 109/l, range 96–730 (p = 0.005). 2 cases responded at the starting dose, while the effective dose was 5 times 106U/d in the others. Minor changes in spleen size were noted, while no significant changes in bone marrow fibrosis occurred. After induction therapy, 3 patients were allocated to maintenance therapy (from 10 up to 34 months). To maintain platelet count lower than 500 times 109/l, the required r‐α‐INF dose was constantly 10 MU/wk, while the same result was not achieved in 1 case with hydroxyurea, 1 g/die. The association with hydroxyurea, 500 mg/die, allowed reduction of the r‐αINF dose to 6 M