Among of the total number of 273 children with different malignancies treated at the Pediatric Oncologic Department in a period of 10 years in 4 boys secondary nonlymphoblastic leukemia was observed. It occured in 2 children with acute lymphoblastic leukemia after 4 and 30 months lasting complete remission and in one child with non-Hodgkin's lymphoma of T-type after 21 months lasting remission. ANLL was also seen in a patient with osteosarcoma after 15 months of unsuccessful cytostatic, surgical and radiotherapeutic treatment. The possibility of initial bilinear leukemia on one hand and the possible effect of the cytostatic therapy on the other hand, mainly of epipodophyllotoxin, which was a part of the chemotherapy in 3 patients, as pathogenic factors of developing of secondary myeloid leukemia are discussed.

        Key words: primary malignancy, secondary acute nonlymphoblastic leukemia, karyotyping, immunophenotyping, epipodophyllotoxins