The karyotype is critical for the evaluation of acute myeloid leukemia (AML) at diagnosis. Cytogenetic abnormalities detected in AML are one of the most powerful independent prognostic factors. It impacts on the choice of treatment in clinical trials. All chromosomes can be targeted, common chromosomal abnormalities are recurrent and may be associated with a cytological well-defined type. In 40% of the cases, the karyotype is normal and must be associated with molecular biology studies that can refine the prognosis. The usefulness of the karyotype is more limited during the follow-up of the patient due to its limited sensitivity, but it is still useful in the clinical management of relapse. Since 2001, the WHO (World Health Organization) classification of hematological malignancies integrates cytogenetic data in the classification of AML. Karyotype is therefore mandatory in the diagnosis of AML.