Summary—Liver peroxisomes of two anuran amphibian species,Rana esculentaandXenopus laevis, were studied in untreated and in clofibrate‐treated adults by means of complementary technical approaches,ie, ultrastructural cytochemistry, cell fractionation and marker enzyme activity assays. In untreated adults, hepatic peroxisomes were found to be very scarce inXenopuswhen compared toRana. Activities of catalase,d‐amino acid oxidase and of the three first enzymes of the peroxisomal β‐oxidation system were detected in the light mitochondrial fractions enriched in peroxisomes and prepared from livers of both species. Administration of clofibrate at a daily dose level of 60 mg (Rana) and 90 mg (Xenopus) during ten days induced a drastic peroxisome proliferation inRanahepatocytes but had no visible effect on the hepatic peroxisomal population ofXenopus. The catalase activity and the peroxisomal β‐oxidation system of liver cells were enhanced inRanaas well as inXenopus. The hepaticd‐amino acid oxidase specific activity was increased inRanawhereas it remained rather constant inXenopus. Taking advantage of the behaviors ofRanaandXenopushepatic peroxisomes, the molecular mechanisms of clofibrate induction are now investigated in the target liver cells of the two amph