In the present study, the expression of two NK-associated antigens (CD56 and CD16) together with six 'classically' considered lymphoid-related markers (TDT,CD19,CD10,CD7,CD2,CD4) has been analyzed by appropriate dual combinations in 265 acute myelogenous leukemia (AML) patients. Among the lymphoid markers, CD4 and CD7 were those most frequently expressed by AML blast cells (58% and 21.6%, respectively) while the incidence of positivity for the other markers was lower: CD19 (7.8%), CD10 (10.9%), CD2 (11.4%), and TDT (11.3%). Regarding NK-associated antigens, CD56 was present in 41% of AML cases analyzed whereas CD16 was detected in only 23%. All but one of the CD16+ cases coexpressed the CD56 antigen. The expression of these antigens was not associated with the degree of cell differentiation assessed either by morphological or immunophenotypical criteria, with the exception of the correlation observed between monocytic leukaemias and the expression of the CD4, CD56, and CD16 antigens. Regarding the prognostic value of the markers investigated, CD56 expression was associated with a tendency for a better outcome whereas CD7 was the only antigen that had an adverse influence on the survival of AML patients.