Cytogenetically unrelated clones are uncommon in hematologic malignancies. We report a case of acute myeloid leukemia, which consisted morphologically of two populations of small and large blasts demonstrating immunophenotypic heterogeneity. Cytogenetic analysis showed 3 karyotypically abnormal clones: 47,XY, +14/45,XY,dic(5;17)(q11;p11),14dmin, and a near-tetraploid clone. In situ hybridization showed that the near-tetraploid clone corresponded to the large blasts, and the near-diploid clones the small blasts, therefore demonstrating a direct relationship between cell size and DNA content. The diverse morphologic, immunologic and cytogenetic heterogeneity observed in our case suggested hematopoietic oligoclonality.