Tetraploidy and near-tetraploidy are observed infrequently in hematologic malignancies, most commonly seen in cases of childhood acute lymphoblastic leukemia, and are associated with large blast size. Four cases of adult acute myelogenous leukemia (AML) with tetraploid or near-tetra-ploid karyotypes are reported, along with review of the related literature. AML subtypes included M1, M1, M4, and M5b. Tetraploidy was determined cytogenetically and confirmed by image cytometry (DNA index 2.0). The subjective impression of large blast size was confirmed by image cytometry, demonstrating mean blast nuclear areas of 237, 177, 203, and 216 microns2, (mean 208 microns2) in the cases with tetraploidy, compared to a mean of 134 microns2 in 10 control cases of AML with diploid or near diploid chromosome patterns. The clinical course was variable in the four cases reported. When compared with previously published cases, the occurrence of tetraploidy or near-tetraploidy in adult AML, unlike childhood ALL, does not appear to define a distinct subgroup in terms of FAB classification or to carry prognostic implications.