An ever increasing attention of clinicists is being focused on nontraumatic clostridal surgical infections. Personal clinical case material consisting of 390 patients with microbiologically proved clostridial infection are subjected to clinical and microbiological investigations aimed at establishing the nature of the infective process. In 377 patients (group one) signs of mixed aerobic-anaerobic polyinfection are clinically documented, fully confirmed by the comprehensive microbiological examinations performed. In 120 patients of this group 162 Clostridida species are isolated, but none of them, including the severest cases, are suspected for gas gangrene presence. In 13 patients of group two presenting clinical picture of a typical gas gangrene, the latter is both demonstrative and impressive. Here the microbiological examinations are absolutely analogical to those in group one which warrants the assumption of the endogenous character of the infective process, leading in turn to inferenceshaving important practical implications and recommendation to modify the antiepidemiological measures with a special reference to the endogenous character of the infective process.