Aim. To assess etiologic factor of Clostridium genus associated infection and its influence on the disease clinical course. Materials and methods. 549 in-hospital patients participated in the study. We evaluated clinical and biochemical parameters of blood, stool frequency or stoma function intensity, feces volume per day and length of in-hospital stay. We performed stool sampling three times: during 48 hours after admission, in case of diarrhea and prior discharge. We evaluated glutamate-dehydrogenase (GDH) and Clostridium difficile toxins A and B by means of immunological assays. All samples underwent cultivation in anaerobic conditions. Results. Analysis of clostridial infection ethiologic factor has revealed 38 (17,9%) cases of clostridial diarrhea associated with another Clostridium species. We discovered Clostridium perfringens in 32 (84%) cases, Clostidium novyi in 5 (13%) cases and Clostidium hathewayi in 1 (3%) patient. Diarrhea severity, clinical and laboratory inflammation markers did not differ significantly depending on the isolated etiological agent of clostridial infection and its titer. Clostridial infection significantly increased in-hospital post-surgery length of stay by 4 days (p < 0,01). Conclusions. Symptoms C. difficile-associated infection could occur not only in case of persisting C. difficile but also in cases of other Clostridium species. Clinical manifestation of C. difficile-associated infection increase in-hospital stay.