We investigated the relationship between interleukin-6 (IL-6) levels and subset profiles of T lymphocyte (T-cell) and macrophage in peritoneal fluid (PF) with or without endometriosis (EM). IL-6 levels in PF with EM were significantly higher than those without EM. IL-6 producing cells with EM were analyzed in each activated mature T-cell (CD3+CD69+) and macrophage (CD14+) were 0.5 and 3.5%, respectively, whereas it was mostly negative in those without EM. Cytotoxic T-cell (CD8+CD11b-) profiles in PF with EM were also quiet different from those without EM. Cellular immunity in the peripheral blood did not change during the course of IVF-ET cycles, although plasma levels of ovarian steroid hormones significantly increased comparing with that in normal ovarian cycles. Cytotoxic T-cell type 1 (Tc1) profiles might be useful predictive values in the pregnancy outcome for infertile patients with EM.