Deletion of chromosome Xq23 has been reported in a number of solid tumors, including soft tissue sarcoma, malignant melanoma, astrocytoma, and adenocarcinoma. The deleted Xq often occurs in a setting of very complex karyotypic changes. A similar abnormality has also been described in rare cases of acute myeloid leukemia (AML) but in no other hematologic malignancies. In this study, we report the occurrence of del(X)(q23) in two cases of AML.