The immune status and profile of HLA antigens of loci A and B were evaluated in 159 patients with reactive arthritis. Reactive arthritis was caused by urogenital chlamydial infection in 64.2% of cases and by Shigella, Salmonella and Yersinia enterocolitica infection in 18.9% of cases. In patients with different etiology of the disease some variations in its course and outcome, immune status as well as in the HLA antigen profile were established that is indicative of genetic determination of the immune response character. The established specific variations in the immune and immunogenetic status of patients with reactive arthritis of different etiology may be used for improving diagnosis and treatment efficacy.