The endothelium plays an important role in the regulation of molecular exchanges between the blood and peripheral tissues. The transport of molecules between tissues must be tightly controlled in order to maintain homeostasis between the different organs of the body. The endothelial transcytosis pathway has been shown to direct the transfer of proteins and solutes and therefore to act as a filtering system. This transport mode has been demonstrated to involve plasma-membrane vesicles that may be transferred with their cargo components from the apical to the basal side of endothelial cells. Among the vesicles implicated in the regulation of transcytosis, caveolae, which are 50 to 100-nm plasma-membrane invaginations, have been reported to play an essential part. In this paper, we review the function of caveolae and their major protein component (i.e., caveolin-1) in the regulation of endothelial transcytosis. The roles of caveolae in vascular diseases, such as atherosclerosis, are discussed.