Although several cytokines and chemokines have been demonstrated to play pivotal roles in the pathophysiological conditions of atherosclerosis, few findings exist regarding the expression and function of cytokine-modulating molecules such as ephrin-Bs and their cognate receptors, EphBs, in human atherosclerosis. Therefore, in the present study, we screened novel genes modulating atherogenesis by cDNA array and quantitatively determined them by real-time RT (reverse transcription)-PCR in human carotid atherosclerotic plaques. Ephrin-B1 and EphB2, key regulators of embryogenesis, were significantly up-regulated in plaques compared with those in adjacent control tissues [ephrin-B1, 0.638 +/- 0.106 compared with 0.831 +/- 0.152, or 130% (P < 0.05); EphB2, 1.296 +/- 0.281 compared with 2.233 +/- 0.506, or 172 % (P < 0.05)]. Immunohistological analysis demonstrated that both ephrin-B1 and EphB2 were expressed in macrophages and T-lymplhocytes in plaques as well as in monocytes, T-lymphocytes and arterial endothelial cells isolated from healthy adults. Interestingly, the extracellular domains of ephrin-B1 and EphB2, the expression of which were both enhanced in stimulated THP-1 cells, significantly inhibited spontaneous (22.5 and 27.6 % respectively; P < 0.01) and MCP-1 (monocyte chemoattractant protein-1)-dependent (29.7 and 22.6% respectively; P < 0.01) migration of monocytes. In conclusion, these results demonstrate that ephrin-B1 and EphB2 are overexpressed in atherosclerotic tissue and might locally regulate cell migration, possibly through modulating cytokine-related chemotaxic activity; however, the functional role of these molecules in atherogenesis should be investigated further.