In this review the recent data about oxygen-depended mechanism of host defense fulfilled by phagocytic cells were presented. The directions of the reactive metabolites oxygen formation and enzymic systems participating in its generation were described in details. The bactericidal characteristics of oxygen reactive metabolites are given, it was marked their role as like as physiologic messengers of inflammation. The differences in realization of the bactericidal activity of neutrophils or macrophages were characterized. The information about role of neutrophils in phagocytes cooperation in infection was analyzed as well as the proof of these cells ability to the synthesis and excretion of bioactive extracellularly substances with low-molecular weight