Endothelial cells play an active role in the maintenance of homeostasis. Endothelial injury can give rise to endothelial dysfunction in which the profile of mediators released by endothelial cells is altered. Among these mediators are factors that participate in the development of many cardiovascular disorders. Some of the most important are the prostanoids, which can modulate the progression of atherosclerosis, arterial hypertension, and angiogenesis. Prostanoids are produced by the sequential actions of cyclooxygenases and specific synthases and exert their actions through diverse cell-surface and nuclear receptors. The profile of prostanoids produced depends on cell type and the changing pathophysiological status, and these factors similarly affect the great array of biological responses elicited by these molecules. The resulting complexity enables extremely subtle and highly complex responses, and this provides opportunities for the development of targeted therapeutic approaches.