This high purity phytanic acid is ideal as an analytical standard and for use in biological systems. Phytanic acid in animals is derived from phytol, a breakdown product of chlorophyll which is caused by bacteria in the gut of ruminant animals. It is predominantly found in ruminant fats and in some fish. In the metabolism of phytanic acid it must first be converted to pristanic acid via alpha-oxidation, due to the presence of the methyl group at the 3-position, before undergoing betaoxidation. Phytanic acid has been suggested as being linked with prostate cancer but there is now evidence against this view.1 In diseases involving peroxisomal impairment the branched chain fatty acids phytanic acid and pristanic acid accumulate in high amounts due to deficiencies in alpha- and beta-oxidation.2 Phytanic acid is a ligand and transcriptional activator of murine liver fatty acid binding protein thereby causing peroxisome proliferation.3