Bone marrow karyotypes were performed in 88 cases of adult acute myelogenous leukemia (AML) at diagnosis and classified NN (normal), AA (abnormal), and AN (mixture of normal and abnormal metaphases). A clear relationship was found between karyotype and complete remission (CR) rate: 58% CR in (NN + AN) cases; 14% CR in AA cases (P less than .009). This relationship was even stronger when only patients under 60 years of age were studied. Considering failures of induction treatment, no relationship was found between the NN/AN/AA classification and a drug resistance. In patients over 60, the worse prognosis could be explained by an inferior ability to tolerate intensive treatment.