Infectious agents were detected in 100% of examined children with Reiter's disease (RD). Chlamydia trachomatis were detected in 98% of cases. In children with RD lesions of joints and eyes often took acute forms with cases of sacroiliitis, early muscular atrophy and conjunctivitis. In 95% of the patients the prostatitis manifestations were detected. In children with RD a rised number of CD lymphocytes in combination with the fivefold rised IL-4 content, an essential increase in the activity of C2-C5 components of the complement and a multiple rised level of PSA were registered.