Bone marrow karyotypes of 78 adult patients with acute myelogenous leukemia (AML) were studied at the time of diagnosis, with special reference to the Sakurai and Sandberg classification (NN, karyotype completely normal; AN, mixture of normal and abnormal metaphases in the karyotype; AA, totally abnormal karyotype). The results showed no difference in complete remission rate (CR) or in survival time between the NN and the AN groups, but highly significant differences between the AA group and the NN and AN groups (whether taken together or separately). When studying the relationship between age and survival time, we found that 59 years of age was a frontier between two homogeneous groups having quite different prognoses. The NN/AN/AA classification had a good prognostic value in patients under 59 years of age. In older patients, no correlation was found between the classification and complete remission rate or survival time.