Endothelial cells of the microvasculature differ both structurally and functionally from endothelial cells of larger vessels. To assess whether these cells also differ in terms of direct cell-to-cell communication, we compared gap junction-mediated intercellular coupling and connexin (Cx) expression in monolayer cultures of bovine microvascular and large vessel (aortic and pulmonary artery) endothelial cells. In confluent monolayers, junctional communication (as assessed by transfer of Lucifer Yellow) was greater between large vessel than between microvascular endothelial cells. Basal levels of connexin 43 (Cx43) and Cx43 mRNA were also greater in large vessel than in microvascular endothelial cells. When monolayers of microvascular endothelial cells were mechanically wounded, junctional communication was increased between migrating cells at the wound edge. In contrast, coupling between large vessel endothelial cells was not increased after wounding. The wound-induced increase in coupling between microvascular endothelial cells was accompanied by an increase in Cx43 and Cx43 mRNA. In contrast, Cx43 expression was unaltered after wounding monolayers of large vessel endothelial cells. These studies revealed differences in basal and wound-induced levels of coupling and Cx43 expression in microvascular and large vessel endothelial cells in vitro, raising the possibility that the role of coupling in endothelial cell function may be different in these different cell types.