A second member of the family of nuclear receptors (Nuclear class 1C, Thyroid Hormone Receptor-like) consists of peroxisome proliferator-activated receptors (PPAR, α, β, γ, and δ). They play essential roles in the regulation of cellular differentiation, development, and metabolism (carbohydrate, lipid, protein), and tumorigenesis of higher organisms. The clinical importance of PPARs originates with fibrates and thiazolidinediones (TZDs), which respectively act on PPAR-α and PPAR-γ. They are used to ameliorate hyperlipidemia and hyperglycemia in subjects with type 2 diabetes mellitus. More recently, proof was found that PPARs also contribute to the regulation of certain physiological activities of the prostacyclin (PGI2) system in cardiovascular tissues[1].