Chronic myeloid leukemia (CML) is a myeloproliferative disease arising from abnormal stem cells and associated with splenomegaly and leukocytosis. Hydroxyurea and interferon alpha are used in treatment very frequently. Behcet's disease (BD) is a chronic, repetitive disease of unknown etiology and associated with mucocutaneous, ocular, vascular and central nervous system involvement. Cases with symptoms of BD have been reported during interferon alpha treatment of CML. However, similar symptoms due to hydroxyurea treatment have been reported in only one case until now.