Objective: to evaluate the indicators of oxidative modification of proteins (OMP) in the patients presenting with secondary osteoarthrosis associated with rheumatoid arthritis (RA) and to determine their dynamics under the influence of the combined treatment with the use of low-intensity laser irradiation (LILI). Material and methods. A total of 50 patients with RA associated with secondary osteoarthritis and 25 healthy subjects were enrolled in this study. The patients of one study sub-group (n=25) were given combined therapy with the use of LLLI, those in the second sub-group (n=25) received only drug therapy. We made use of the VAS and DAS 28 scales to estimate dynamics of pain and compared serum OMP in the patients and healthy subjects. Results. The analyses of the data obtained demonstrated the increased OMP in the patients with RA in comparison with the healthy subjects. The patients of sub-group 1 experienced a significant decrease in the clinical parameters of pain based on the VAS and DAS 28 scales accompanied by the marked reduction of OMP. In sub-group 2, the patients also exhibited the statistically significant dynamics of these indicators, but it was less pronounced than in sub-group 2. Conclusion. The patients presenting with rheumatoid arthritis are characterized by the elevated level of protein oxidative modification, a marker of oxidative stress. LILI introduced in the combined treatment of the patients with RA not only increases the anti-inflammatory and analgesic effects but also has the antioxidant properties.