According to WHO, several T-cell immunophenotypic markers may be aberrantly expressed in acute myeloid leukemia (AML). TdT may be expressed in greater than one-third of cases, and CD2 and CD7 may be expressed frequently at low intensity; however, the T-cell lineage specific antigen CD3 is usually absent. In this investigation, 30 cases of AML were evaluated for CD2, CD3, CD5, CD7, CD8 and TdT expression, and mean fluorescence intensities (MFI). Of the 3 (10%) cases positive for CD3 and CD8, 1 was bright (MFI>501), and 2 cases were moderate. TdT was moderately expressed in 4 (13.3%) cases with MFI values between 301 and 500. CD2 and CD5 were positive in 5 (16.7%) cases. While CD2 was moderate in all 5 cases, CD5 was bright in 3, moderate in 1 and dim in 1. Of the 15 (50%) cases positive for CD7, 9 were bright, 5 were moderate, and 1 was dim with a MFI value between 201 and 300. These data indicate that CD2 and CD7 may be frequently expressed at greater intensities than WHO specified. These results point to the need for a more extensive study to evaluate the potential prognostic significance of aberrant T-cell marker expression in AML.