Gap junctions allow the direct exchange of ions and small molecules between cells in contact, thus coordinating physiological processes such as cell growth and differentiation. We have recently demonstrated increased expression of the gap junction protein connexin43 (Cx43) in specific subsets of cells in atherosclerotic lesions. Because the development of atherosclerosis depends critically on paracrine cell-to-cell interactions, we hypothesized that direct intercellular communication via gap junctions may be another factor controlling atherogenesis.