A 29-year-old man with chronic myeloid leukemia and two successfully treated blast crises exhibited ocular symptoms. Eighteen months after the diagnosis of leukemia he presented with unilateral hyperplastic iris stroma, anterior chamber inflammation and vitreous infiltration. Uveitis was diagnosed tentatively, and local therapy was begun with corticosteroids. Because the findings remained unchanged an invasive diagnostic evaluation followed. Although iris biopsy revealed only unspecific mononuclear cell infiltration (mainly T-lymphocytes), selectively aspirated vitreous material contained myeloid cells of different stages of maturation and blast cells. Peripheral blood, liquor and bone marrow showed no signs of acceleration or transition of the primary disease. Thus, an extramedullary blast crises with isolated vitreous infiltration was diagnosed.