Myonecrosis remains one of the severest manifestations of skin and soft tissue infections. Clostridia (C. perfringens, C. novyi, C. septicum, C. sordellii, C. histolyticum) are dominant and Staphylococcus aureus, Streptococcus pyogenes, Bacillus cereus, and Bacteriodes fragilis are much less in the etiology of myonecrosis. Cases of gas gangrene have recently become more frequent among injection drug users all over the world. Russia has become the largest opiate market in Europe and consumption of these narcotic drugs is annually growing. In the Russian Federation, a larger number of injection drug users uniquely results in a rise of cases of Clostridium- and mixed flora-induced myonecrosis. Gas gangrene in HIV-positive drug abusers seems to rapidly progress to multiple organ failure and to show high death rates, rather than to develop a localized form. The analyzed case of mixed flora-induced gas gangrene is of interest to physicians of any specialties who can encounter this wound infection in HIV-positive patients.