The peroxisome proliferator-activated receptor alpha (PPAR ) is a ligand-activated transcription factor involved in the regulation of a variety of processes, ranging from inflammation and immunity to nutrient metabolism and energy homeostasis. PPAR serves as a molecular target for hypolipidemic fibrates drugs which bind the receptor with high affinity. Furthermore, PPAR binds and is activated by numerous fatty acids and fatty acid-derived compounds. PPAR governs biological processes by altering the expression of a large number of target genes. Accordingly, the specific role of PPAR is directly related to the biological function of its target genes. Here, we present an overview of the involvement of PPAR in lipid metabolism and other pathways through a detailed analysis of the different known or putative PPAR target genes. The emphasis is on gene regulation by PPAR in liver although many of the results likely apply to other organs and tissues as well.