Pyo-inflammatory diseases continue to be one of the topical problems of modern medicine. Their etiological agents are opportunistic microorganisms among which non spore-forming anaerobes are prevalent in the normal microscopic flora. They cause a pathological process when the body's immunity is decreased. The authors consider the biological features of this group of bacteria, epidemiological and pathogenetic aspects, the problems of laboratory and clinical diagnosis of non clostridial anaerobic infection and outline immediate steps to be taken to solve the problems.