Peroxisome proliferator activated receptors (PPARs) are transcription factors only recently discovered. Nevertheless, the interest surrounding their study has involved and involves a continuously growing number of researchers. This is due to the role that PPARs play in the understanding of the pathophysiology of clinical conditions such as obesity, diabetes, atherosclerosis, and angiogenesis. Lipid and glucidic metabolism, synthesis of cytokines, adhesion molecules, coagulation factors, fibrinolysis, are only few of the several processes controlled by PPARs. In this review the more recent acquisitions on PPAR mechanisms of action will be described. The clinical implications that their activation/deactivation induce will be also evaluate. Particular emphasis will be placed on their role in the control of the physiology of lipid and glucidic metabolism, as well as in the pathophysiology of inflammatory and atherosclerotic processes.