The aim of the investigation was a comparative study of changes in the level of the complement and concentration of circulating immune complexes (CIC) in blood and lymph at the Arthus and Overy phenomenon.Experiments were conducted in three series. As a control group, the concentration of circulated immune complexes and level complement in the blood and lymph of intact animals was investigated. The concentration of immunocomplexes circulating in blood and lymph was investigated by the method of sedimentation of proteins by 3.5% poliethilenglucolum. For the definition of the titer of the complement in blood and lymph, the Reznikov's method is applied. At the statistical processing of the received data, methods of descriptive statistics, and rank criterion of Wilcoxon-Manna-Whitney are applied. The average value of received data is applied in a format of M±m (min-max) [11].Results. Both in the sensitization and resolution stages of the Arthus and Overy phenomenon, the concentration of circulating immune complexes (CIC) increases, but this increase is more pronounced in animals with reproduced Arthus phenomenon. The complement titer decreased in the period of sensitization and in the period of the Artyus phenomenon. And in the period of Overy's phenomenon, it decreases more expressively.