The results of biochemical studies of the antioxidant preventive system are given in the article. They were determined by the activity of superoxide dismutase (SOD), catalase, ceruloplasmin, glutathione peroxidase, glutathione reductase and reduced glutathione on the 7th, 14th and 30th days of development of experimental periodontitis. It is shown that the generation of reactive oxygen species is associated with an increase in the activity of immune processes, which becomes more potent and provides a protracted character to the inflammatory process in the periodontal tissues. In that is paid attention to the characteristic dynamics of changes in the activity indices of lipid peroxidative processes and the antioxidant protective system in the development of experimental periodontitis. In the early period of development of experimental periodontitis, that is, on the 7th day, the activity of SOD in the blood serum decreased, and later, on the 14th and 30th days, it increased. On the 7th day of the experiment, an increase of the catalase activity and ceruloplasmin in the blood serum was found, respectively) in comparison with the control. On the 14th day catalase activity and ceruloplasmin was decreased as compared to the group of animals examined on the 7th day of the experiment. On the 30th day their levels in the blood serum still is remained decreased. The dynamics of indices reduced glutathione were similar to the dynamics of superoxide dismutase activity, that is, on the 7th day of the experiment there was a decrease. The partial increase enzymic activity of the glutathione system (glutathione peroxidase, glutathione reductase) occurred on the 14th day of the inflammation but subsequently these parameters became the opposite of changes. It is established that in the conditions of formation and course of experimental periodontitis the intensity of antioxidant protection activity varies.