Methyl-2-[4-(p-chlorophenyl)-phenoxy]-2-methylpropionate (methyl clofenapate) a hypolipidemic compound, was administered in the diet (0.03%) for 2–5 weeks to male wild type (Cs^a strain) mice. Electron microscopic examination of the kidneys revealed a significant increase in the number of single membrane limited organelles in cells of the P₁, P₂ and P₃ segments of the proximal convoluted tubule. Catalase was localized in these organelles cytochemically by incubating tissue in alkaline 3,3’-diaminobenzidine medium; which enabled their identification as peroxisomes. There was no increase in lysosomes in the renal tubules of methyl clofenapate treated animals. It is not certain if the presence of large number of peroxisomes in the proximal tubular epithelium causes impairment of renal function.