Macro- and microvascular disorders currently represent the principal causes of morbidity and mortality in patients with diseases involving the cardiovascular system, such as atherosclerosis, hypertension, stroke, and diabetes. Abnormal vasomotor responses and impaired endothelium-dependent vasodilation have been demonstrated in a number of vessels in a variety of animal models and in humans with such diseases. Endothelial dysfunction plays a key role in the development of these diseases, yet the genesis of this endothelial dysfunction and its associated vasomotor abnormalities remain poorly understood. Peroxisome proliferator-activated receptor (PPAR)γ is a nuclear receptor and transcription factor in the steroid superfamily, and PPARγ agonists (the thiazolidinediones) are used clinically to treat type 2 diabetes. Recent studies have revealed that as well as being involved in adipogenesis and in increased sensitivity to insulin, PPARγ plays critical roles in the vasculature. In the present review, we discuss the beneficial effects of PPARγ agonists on vasomotor activities, focusing in particular on endothelium-dependent relaxation in vessels affected by cardiovascular diseases.