Leptin is an adipocyte-derived hormone that plays a major role in the regulation of energy homeostasis through its action in the central nervous system. Leptin also acts on several peripheral tissues, including the vascular endothelium. The leptin receptor has been identified in endothelial cells. Leptin action on the endothelium modulates several physiologic processes, with potential implications in pathophysiologic diseases associated with obesity. Leptin stimulation of angiogenesis has attracted attention because of its potential involvement in retinopathy and atherosclerosis. Leptin activation of endothelial oxidative stress also has implications in atherosclerosis and inflammation. However, data on the impact of the endothelial effect of leptin on arterial pressure are contrasting. Although some investigators have shown that leptin action on the endothelial nitric oxide system tends to decrease arterial pressure, others have shown no contribution from the endothelial effect of leptin to the control of arterial pressure. Further characterization of the endothelial effects of leptin will, it is hoped, help in the understanding of the different pathophysiologic diseases associated with obesity.