The necrotizing soft tissue infection caused by anaerobic microorganisms or by mixed aerobic-anaerobic flora is one of the most severe infections in surgical practice with a mortality rate up to 75%. Of great importance for successful treatment are the early diagnosis followed by aggressive debridement and adequate antibacterial therapy. Depending on the studies of 358 isolates made in the Clinic of Septic Surgery, we specify the most often used antibiotics in cases of severe anaerobic surgical infection. It is established that the incidence of this severe infection is unpredictable and its spreading depends on the immune answer the concomitant illnesses and the previous undertaken surgeries of the patient.