PROBLEM: There is increasing evidence that decidual lymphocytes play a major role in local interactions at the fetomaternal interface. METHOD: In this paper we use two-color flow cytometry to delineate the phenotype of lymphocytes obtained from human early decidua by mechanical dispersal technique. RESULTS: The most abundant decidual lymphocytes expressed CD7, CD38, CD56, and CD2 markers, relatively small proportions of CD3+, CD8+, CD4+, CD16+, CD45RA+, CD11b+, and Leu8+ cells were also present. The vast majority of decidual CD7+ lymphocytes expressed CD38, CD2, and CD56 markers and were CD3-, CD8-, CD16-, and CD57-. Decidual CD3+ lymphocytes were weakly staining for TCR alpha/beta, lacked T-cell receptor (TCR) gamma/delta molecules, and approximately 40% of them expressed HLA-DR. All decidual CD8+ lymphocytes were CD2+ and the majority of them expressed CD38, CD56, and CD7 markers and were CD3- at the same time CD8+CD7- lymphocytes were found in decidua. According to the expression of the CD45RA marker, decidual CD8+ lymphocytes could be divided into two subsets: CD8+CD45RA+CD56+ and CD8+CD45RA-. CONCLUSIONS: These data clearly demonstrate that decidual lymphocytes display phenotypical features different from those of their counterparts in peripheral blood.