Abstract: Cytogenetic abnormalities at diagnosis are important prognostic indicators in acute myeloid leukemia (AML). AML is categorized into 3 risk groups according to cytogenetic abnormalities; favorable, intermediate, and unfavorable. A new cytogenetic risk group called the monosomal karyotype (MK) had been identified in AML with unfavorable-risk cytogenetics. The MK was reported to be associated with a dismal prognosis. The objective of this retrospective study was to analyze the type of chromosomal abnormalities found in adult AML patients with MK at diagnosis.