The scientific literature does not discuss how the oxygen-dependent and oxygen-independent mechanisms of bactericidal activity of peripheral blood phagocytes relate to each other. For example, does oxygen-dependent and oxygen-independent bactericidal mechanisms act by themselves and independently? Or do they interact, potentiating each other's action? This work aimed to study the cooperation (clarification of the participation) of oxygen-dependent and oxygen-independent bactericidal systems of peripheral dog' blood neutrophils in the phagocytosis process. The mechanism of oxygen-dependent bactericidal activity of neutrophils was visualized in the NBT test. Study of the oxygen-independent bactericidal activity mechanism of neutrophils flowing through bactericidal proteins by Pigarevsky. Cytological preparations had been examining under immersion objective. Obtained results confirmed the well-known fact that a certain amount of peripheral blood granulocytes contains substances responsible for oxygendependent and bactericidal activity. These two mechanisms of bactericidal activity, responses different cells. In phagocytosis, bactericidal substances gradually accumulated around the phagocytosed material and, after a while, completely impregnated it. In addition, particles phagocytosed by leukocytes containing cationic proteins were also gradually enveloped by the latter. However, in the research process, it was not established that these proteins penetrate deeply into phagocytosed particles. In the studied preparations, several such variants of the interposition of NBTpositive phagocytes and phagocytes containing cationic proteins are visualized, suggesting that these cells can interact in phagocytosis. It was found that different granulocytic cells have oxygen-dependent and oxygen-independent bactericidal activity. Also, bactericidal activity is exposed to bactericidal action by leukocytes, responsible for the oxygen-independent activity.