The farnesoid X receptor (FXR; NR1H4) is a ligand-activated transcription factor that regulates bile acid and lipid homeostasis, and is expressed in the vasculature (Bishop-Bailey et al., 2004). The migration of vascular smooth muscle cells from the tunica media to the sub-endothelial region is a key event in the development and progression of atherosclerosis. Matrix metalloproteinases (MMP) play a critical role in these processes of SMC migration. We have recently showed that FXR ligands inhibit MMP-2 and -9 expression and activities in rat aortic smooth muscle cells (RASMC; Li et al., 2006). We have therefore investigated whether FXR could regulate platelet-derived growth factor (PDGF)-BB or IL-1β-mediated RASMC migration. RASMC culture was as previously described (Bishop-Bailey et al., 2004). Cell migration assays were performed over 72h using growth factor reduced Matrigel-coated (diluted 1:2 in serum-free DMEM) polycarbonate filters (8µm pore size, Transwell; Corning). Cells invading to the lower chamber were trypsinized and counted on a Casy 1 counter (Sharfe System GmbH Retlingen, Germany). The FXR ligand, 6α-ethyl-chenodeoxycholic acid (6ECDCA; 30µM) or vehicle was added to RASMC for 1h before plating and were present throughout the experiment (Thomas et al., 2001). 25ng/ml PDGF-BB or 10ng/ml IL-1β was placed in the lower chamber to induce migration. PDGF-BB but not IL-1β induced RASMC migration. 6ECDCA reduced both the basal and the PDGF-BB induced migration of RASMC (Figure 1). FXR activation blocks smooth muscle cell migration. FXR may therefore be a novel regulator of vascular remodelling.