Purpose : Inflammatory white blood cells are related to semen quality, affecting fertility In these cases, inflammatory cytokines are present in increased quantities, and this increase may be related to sperm motility. We examined changes in measures of motility after administration of cytokines to sperm in vitro. Materials and Methods : Semen from 30 healthy men were obtained. With the swim-up procedure, actively motile sperm were isolated and incubated in Ham's FIO culture medium. Interleukin (IL)-lα (1 ng/mL), IL-6 (1ng/mL), IL-8 (10 ng/mL), or tumor necrosis factor (TNF)-a (10 ng/mL) was added, and measures of sperm motility were examined after 5 and 24 hours using the Hamilton-Thorns computer semen analysis system. These measures were expressed as a percentage of the values before incubation. Results : The decreases of the average path velocity (VAP) in the IL-lα-treated and IL-8-treated specimens after 24 hours are statistically significant. None of the decrease in values for straight-line velocity (VSL) is statistically significant. There were statistically significant decreases in the curvilinear velocity (VCL) in IL-6-treated and TNF-lα-treated specimens after 24 hours. None of the changes in the lateral head displacement (ALH) or the beat cross frequency (BCF) was statistically significant. Conclusion : The administration of cytokines decreases sperm motility in vitro. It is suggested that seminal cytokines may affect sperm motility in vivo.