It was studied the activity of superoxide dismutase, glutathione peroxidase, glutathione reductase, and contents of malondialdehyde and hydroperoxide lipids in the tissues of skeletal muscles, heart, lungs, testicles in the piglets of 1-, 3-, 5- and 10-days age. It was found, that tissues of 1-days piglets characterized by high contents of products of hydroperoxide lipids and activity of superoxide dismutase by low activity of glutathione peroxidase and glutathione reductase. The products contents of hydroperoxide lipids in piglets tissues in the period of 1 to 10-days age reduced. The activity of enzymes of antioxidant system depends from stage of postnatal adaptation and from the kinds of tissues.