The processes of lipid peroxidation, oxidative modification of proteins, the state of antioxidant protection system enzymes and fatty acid composition of liver lipids were investigated in rats with streptosotocin-induced diabetes. The development of diabetes is accompanied by oxidative stress, which results in the activation of lipid peroxidation processes and the increase in the amount of nitrogen oxide and the activity of antioxidant protection system enzymes. The increase of the amount of saturated fatty acid and fall in the amount of unsaturated fatty acid has been detected. The rise of the processes of protein oxidation was established, which can lead to loss of their biological activity.