The confirmed advantageous effects of oxygen/ozone therapy in several clinical conditions stimulated experimental studies on effects of the therapy in rats with an induced septic shock. The studies were conducted on adult male rats of Wistar strain. Four groups of the animals, each of 15 rats, included: I--control group, (C); II--animals intraperitoneally administered with O(2)/O(3) (CO), III--rats given of Escherichia coli endotoxin (lipopolysaccharide-LPS) (CL), IV--rats administered with the lipopolysaccharide plus administered with the oxygen/ozone mixture (OL). Activities of catalase and superoxide dismutase and of free radical reactions were estimated. The exposure to LPS augmented activities of SOD and of catalase in liver, lungs and heart. In all the examined organs LPS induced significant changes in levels of free radicals. Except of the lungs, parallel administration of the rats with LPS and ozone/oxygen revoked development of the alterations. The obtained results point to a strong, stabilizing and regenerative effect of ozonotherapy.