Peroxisomes represent cell organelles present in both unicellular eukaryotes and most of the animal and plant cells. Peroxisomes contain about 50 enzymes with high variability in spectrum and quantity, depending on nutritional conditions and presence of some xenobiotics (peroxisome proliferations). New peroxisomes are formed after the protein intake by splitting of the existing peroxisomes or de novo. Biogenesis of peroxisomes requires cytosolic proteins, membrane transporting proteins, and the typical groups of amino acids in polypeptide chains, which have the character of topogenic signal--PTS (peroxisomal targeting signal). PTS signal is based on the terminal tripeptide, formed usually by amino acids serine, lysine and leucine (SKL tripeptide--PTS1) or by the N-terminal PTS2 with amino acid sequence Arg-Leu/Ile-XXXXX-Gln/His-Leu (X is any amino acid). Biogenesis of peroxisomes requires also special membrane proteins--peroxins, which are coded by PEX genes. These proteins act as homo- or heterodimes, they belong to ATP transports, and determine efficacy of the peroxisome biogenesis. Nuclear gene expression is regulated by nuclear receptors activated by peroxisome proliferators (PPAR-proxisome proliferators activated receptors). C-domain of the receptor binds to the specific region of the promotors of peroxisome genes (PPREs-Peroxisomal proliferator response elements), often with tandem arrangement of sequences TGACCT. Polyunsaturated fatty acids represent the effective natural regulator of the peroxisomal gene expression.