Trichomonas vaginalis commonly causes vaginitis and perhaps cervicitis in women and urethritis in men and women. Macrophages are important immune cells in response to T. vaginalis infection. In this study, we investigated whether human macrophages could be involved in inflammation induced by T. vaginalis. Human monocyte-derived macrophages (HMDM) were co-cultured with T. vaginalis. Live, opsonized-live trichomonads, and T. vaginalis Iysates increased proinflammatory cytokines, such as TNF-${alpha}$, IL-$1{eta}$, and IL-6 by HMDM. The involvement of nuclear factor (NF)-${kappa}B$ signaling pathway in cytokine production induced by T. vaginalis was confirmed by phosphorylation and nuclear translocation of p65 NF-${kappa}B$. In addition, stimulation with live T. vaginalis induced marked augmentation of nitric oxide (NO) production and expression of inducible NO synthase (iNOS) levels in HMDM. However, trichomonad-induced NF-${kappa}B$ activation and TNF-${alpha}$ production in macrophages were significantly inhibited by inhibition of iNOS levels with L-NMMA (NO synthase inhibitor). Moreover, pretreatment with NF-${kappa}B$ inhibitors (PDTC or Bay11-7082) caused human macrophages to produce less TNF-${alpha}$. These results suggest that T. vaginalis stimulates human macrophages to produce proinflammatory cytokines, such as IL-1, IL-6, and TNF-${alpha}$, and NO. In particular, we showed that T. vaginalis induced TNF-${alpha}$ production in macrophages through NO-dependent activation of NF-${kappa}B$, which might be closely involved in inflammation caused by T. vaginalis.