The development of various kinds of autoimmune disease as a result of interferon-alpha (IFN-alpha) therapy has been reported among chronic myeloproliferative disorders(CMPD) including chronic myeloid leukemia(CML). Therefore, we investigated the frequency of autoimmune disorders in 33 patients with hematopoietic diseases treated with IFN-alpha in our department. Thirty-three patients (12 females, 21 males) included cases of CML (n = 23), essential thrombocythemia (ET) (n = 1), multiple myeloma (n = 8), and hypereosinophilic syndrome (HES) (n = 1). Autoantibodies (ANA, dsDNA, and RAPA), thyroid grand functions, and coagulant functions were examined. Twenty-five out of 33 patients were treated with natural IFN-alpha, and 8 patients were treated with recombinant IFN-alpha 2b (rIFN alpha-2b). Three patients were treated with IFN and anticancer agents. Antinuclear antibodies were detected in 2 of 33 patients. RAPA and anti-thyroglobulin antibody became positive in 3 and 4 patients, respectively. Ten patients showed low serum levels of either free T3 and/or free T4. However, none of them showed any clinical symptoms for developing autoimmune diseases. In addition, circulating anticoagulant antibodies were detected in 3 of 23 patients with CML treated with rIFN alpha-2b, but in no cases treated with natural IFN-alpha. Although none of the patients developed autoimmune diseases, we concluded that patients receiving IFN therapy should be carefully monitored for clinical signs and symptoms of autoimmune disorders.