In the past few years, much has been learned about the metabolic functions of peroxisomes. These studies have shown that peroxisomes play a major role in lipid metabolism, including fatty acid beta-oxidation, etherphospholipid biosynthesis, and phytanic acid alpha-oxidation. This article describes the current state of knowledge concerning the role of peroxisomes in these processes, especially in relation to various peroxisomal disorders in which there is an impairment in peroxisomal lipid metabolism.