In the present work, we investigated the Th1 and Th2 cytokine patterns secreted by infiltrating endometrial lymphocytes from fertile women and from patients with recurrent spontaneous miscarriage (RSM). Moreover, we also analyzed the expression of cytokines in the whole endometrium from fertile and RSM women. Furthermore, we investigated the expression of the activation marker signaling lymphocytic activation molecule (SLAM) a cell surface glycoprotein expressed on lymphocytes that upon engagement boosts IFN-gamma production. Our results showed a slight increase in IL-10 expression in the endometrium of some fertile women, although no significant differences were found in IFN-gamma and IL-5 expression. In contrast, analysis of IFN-gamma production by polyclonal activated lymphocytes from endometrium and/or peripheral blood from fertile women showed a significant increase compared to RSM. Analysis of SLAM protein expression in luteal phase endometrial samples showed a significant increase in the levels of the receptor in RSM women compared to fertile women. These results correlated with a significant augmentation of SLAM levels in peripheral blood T-lymphocytes from RSM patients. Interestingly, after treatment of RSM patients with paternal mononuclear cells, surface-SLAM-expression in T-cells from RSM patients significantly decreased up to levels comparable to those of fertile women. Taken together, our results suggest that endometrial cells have not a defined pattern-cytokine-production under pre-implatatory conditions, and SLAM might be a potential marker for the diagnosis of RSM and an indicator useful to follow up the patient response to allogeneic immunotherapy.