Lipid metabolism and indices of oxidation processes obtained during examination of specimens of Antarctic toothfish Dissostichus mawsoni (Perciformes: Nototheniidae) caught in the Ross Sea are given. Blood plasma, tissues mesonephric kidney, liver and spleen were studied for the content of total lipids and lipid composition, products of lipid peroxidation and level of antioxidant protection. Biochemical status of immune organs depending on the structural and functional characteristics of tissues was established.Lipid metabolism and indices of oxidation processes obtained during examination of specimens of Antarctic toothfish Dissostichus mawsoni (Perciformes: Nototheniidae) caught in the Ross Sea are given. Blood plasma, tissues mesonephric kidney, liver and spleen were studied for the content of total lipids and lipid composition, products of lipid peroxidation and level of antioxidant protection. Biochemical status of immune organs depending on the structural and functional characteristics of tissues was established.