Thirty-three patients presenting with orbito-ocular granulocytic sarcoma (OOGS) and acute myelomonocytic leukemia (AMML) were diagnosed in Turkish children from 1963 to 1983. OOGS, characterized by exophthalmos, chemosis and orbital masses, was observed in 33 (27.2%) of 121 AML patients compared with 41 children of AMML without ophthalmic tumors during the same period. Eye tumor and bone marrow aspirates were also studied under light and electron microscopies. The comparison of the hematological parameters did not indicate any statistical difference between the groups. Despite similar chemotherapy regimens administered to all patients, the mean survival time was 8.7 months in the OOGS group, which is significantly shorter compared to those without OOGS (28.6 months) (p less than 0.01). These cases may be classified as a "high risk" subgroup of childhood AMML.