Secondary chromosome aberrations in de novo acute myeloid leukemia ( AML) are less specific and occur in addition to the primary chromosome abnormalities. Secondary chromosome aberration in acute nonlymphocytic leukemia has been recognized for many years as the most serious long-term complication of malignant disease. Our aim in this study was to focus on patients with AML associated with secondary chromosomal abnormalities in 127 consecutive Iranian leukemia patients. Methotrexate (MTX) cell synchronization and 24h non-stimulated cultures of bone marrow cells were applied to determine the incidence of chromosomal aberrations and association of specific primary and secondary chromosome anomalies according to French American British (FAB) morphological subtypes. The distribution of the secondary changes was clearly non-random. The most frequent numerical changes were –X, - Y, -7, +8 , -10 and +22 and the most common structural aberrations were i(17q), 9q-, dicentric and marker chromosome. We believe this report is the first for de novo AML patients showing secondary chromosomal abnormalities which are quite non-random. The findings could contribute to widening knowledge of related chromosomal abnormalities.