Inflammatory Bowel Disease (IBD) is a group of disorders that are characterised by chronic intestinal inflammation. While the etiology of IBD is not yet fully understood, infiltration of monocytes to the mucosa and the release of proinflammatory mediators is thought to play an integral role in disease progression. Among the mediators released from monocytes is IL-8, a known neutrophil attractant that drives mucosal inflammation. Ursodeoxycholic acid (UDCA) is a naturally-occurring secondary bile acid that is well-established to exert cytoprotective and anti-inflammatory effects. Here, we investigate the effects of UDCA in regulating IL-8 release from monocytes. IL-8 release from U937 monocytes was induced by treatment with either lipopolysaccharide (LPS) [1 µg/mL], or the pro-inflammatory cytokine, tumour necrosis factor α (TNFα) [5 ng/mL], in the absence or presence of UDCA. Supernatants were analysed for IL-8 release by ELISA. IL-8 mRNA levels were measured by qPCR. Levels of phospho-p38 MAPK, phospho-p65 and phospho-TRAF2 were measured by western blotting. Cellular toxicity was determined by LDH release. Statistical analyses were performed by one way ANOVA with the Newman Keul’s post-test. Treatment of U937 monocytes with either TNFα or LPS induced levels of IL-8 from 195 ± 82 pg/mL to 2,343 ± 282 (n=3) and 26,017 ± 394 pg/ml (n=3), respectively. Co-treatment with UDCA [100 µM] reduced TNFα-driven IL-8 release from 2,343 ± 282 to 1,684 ± 243 (n=5) but did not have an effect on LPS-driven IL-8 release (n=7). Similarly, UDCA was found to reduce TNFα but not LPS-induced IL-8 mRNA levels (n=4). At the concentrations employed, UDCA did not exert toxic effects, as determined by LDH release (n=3). Analysis of the signalling pathways involved revealed that both TNFα and LPS induced phosphorylation of p38 MAPK. However, UDCA did not alter these responses (n=3). Both TNFα and LPS induced phosphorylation of p65, a marker of NFkB activation, while the NFkB inhibitor, BMS-345541 [10 mM], attenuated IL-8 release in response to both agonists (n=5). Interestingly, co-treatment with UDCA attenuated TNFα-, but not LPS-, induced phosphorylation of p65 (n=4). Finally, we examined TRAF2, a protein involved in mediating TNFα induced actions in monocytes. We found that TNFα, but not LPS, induced phosphorylation of TRAF2, while treatment with UDCA attenuated this response (n=7). UDCA specifically inhibits TNFα-induced IL-8 release from monocytes by a mechanism that appears to involve inhibition of TRAF2 and NFkB activation, In vivo, such effects would be expected to dampen mucosal immune responses and therefore suggest that UDCA may be useful as a new approach for treatment of IBD.