Objectives: Seminal plasma elicits recruitment of immune cells into the cervix. It increases in mice in vivo and in humans in vitro the endometrial epithelial expression of those cytokines and growth factors, which play an essential role in implantation. To analyse if the stimulatory effect of seminal plasma correlates to the quality of the sperm count, the immunomodulatory potential of seminal plasma of fertile and infertile men was studied. Study design: Seminal plasma from 34 volunteers with normal sperm count und from 28 men with oligozoospermia or asthenozoospermia was studied. Firstly, the concentrations of IL-6, IL-8, VEGF, TNF alpha IL-1 beta, TGF beta 1 and G-CSF were analysed by ELISA. Secondly, the immunomodulatory potential was studied by bioassays. Bioassays were set-up by isolation of peripheral mononuclear blood cells (PMBC), sensitized by stimulation with LPS. The assays were incubated with seminal plasma of both patient groups and secretion of IL-6, IL-8 and TNFa was analysed by ELISA. Results: IL-6, IL-8, VEGF, TNF alpha IL-1 beta, TGF beta 1 and G-CSF were detected in seminal plasma. The bioassays revealed a significant increase of IL-6 and IL-8 and a decrease of TNF alpha by incubation with seminal plasma. The concentrations of all factors and the stimulatory and inhibitory potential of seminal plasma from men with oligozoospermia, asthenozoospermia and normozoospermia were not significantly different in ELISA- and bioassays. Conclusion: The experiments revealed a similar immunomodulatory potential of seminal plasma from men with normal and abnormal sperm counts, suggesting that male infertility is probably not caused by differences in the activity of seminal plasma. (C) 2007 Elsevier Ireland Ltd. All rights reserved.