Peroxisomes are becoming more and more attractive. This interest has grown up due to some key metabolic functions (i.e. very long chain fatty acid specific beta-oxidation, prostaglandins and polyamines catabolism, and first reactions in plasmalogen synthesis, as well as biliary salts) and to their strong response to peroxisome proliferators which can promote hepatocarcinogenesis in rodents. This mini-review comments recent breakthrough which is the discovery of peroxisome proliferator activated nuclear receptors (PPAR's) from the steroid receptor superfamily. Mouse PPAR and Xenopus PPAR's (alpha, beta and upsilon) activate the rat peroxisomal acyl CoA oxidase gene by recognition of specific responsive elements containing the 5'flanking "TGACCT" repeated sequence in the -560 upstream region. Such mechanism is involved in the control of peroxisomal beta-oxidation pathway.