Leukemia is a hematopoetic tissue tumor with a primary lesion of the bone marrow, where the morphological substrate is the blast cell. Chromosomal and molecular genetic aberrations play a major role in the acute leukemia pathogenesis, determing the morphological, immunological and clinical features of the disease. Our study was aimed to to analyze retrospectively the structure and frequency of chromosomal aberrations in children with initially diagnosed acute leukemia. Material and methods. Medical histories retrospective analysis of children charged to oncohematology department of the «Scientific Center of Pediatrics and Pediatric Surgery» in Almaty for the period 2015 - 2017 was carried out. 310 histories with primary diagnosed acute leukemia were studied. Results and discussion. Among 310 patients different chromosome aberrations were isolated in 158 patients (51%) during cytogenetic and molecular cytogenetic (in situ hybridization) studies of bone marrow blast cells. A normal karyotype was observed in 102 patients (33%). Conclusion. The lymphoblastic variant of acute leukemia was determined in 75.5%, that indicates its leading role in AL structure among the children of different ages. AML was determined in 22.6% of all OL cases. The most frequent chromosomal rearrangement in ALL patients was blast cell chromosome hyperdiploidy (10,6%) and t(12;21)(p13;q22)/ETV6-RUNX1,which was detected in 37 (16%) patients. The most frequent AML abberation was t (8;21) (q22;q22)/RUNX1-RUNX1T1, identified in 15 (21.4%) patients. Keywords: acute leukemia, bone marrow, blast cells, karyotype, chromosomal aberrations, cytogenetic study.