Investigation was carried out for studying the role of lipid peroxidation (LP) in the genesis of destructive process in the abdominal cavity. The model of experimental peritonitis was made on the dogs. According to the concentration of fat acids conjugates with double couplings (diene conjugates--DC), malondialdehyde (MDA) the LP activity was discovered. Simultaneously the activity of ceruloplasmin (CP), superoxide dismutase activity of plasma, total proteolytic blood activity, summary indicators of antioxidants plasma status and the level of medium-mass molecules was indicated. It was established that LP activation began in the first hours of peritonitis development yet, concentration of LP metabolites (MDA and DC) in plasma increased during disease progressing. CP and superoxide dismutase activity of plasma decreased. Total proteolytic blood activity and level of medium-mass molecules increased after the growth of LP intensity.