Clostridium difficile(CD) infection is typical nosocomial infection. CD is the cause of 20 % of post antibiotic diarrhea. Approximately 20 % of patients after metronidazol or vankomycin therapy develop recurrent disease. Abdominal pains, fever, leucocytosis, diarrhea , sometimes haemorhagic,and typical pseudomembranes in colonoscopy are diagnostically important. Cell-culture cytotoxin assays to detect toxin A,and B, pulsed-field electrophoresis or PCR are for laboratory diagnosis most important. CD is usually susceptible to metronidazol and vankomycin in peroral, jejunal or as an enema application. Prophylactically probiotics Sacharomyces boulardii and lactobacillus spec., adhesive polymers (Tolevamer) or immunotherapy are recommended. Institutional outbreak of CD associated diarrhea especially in hospitals with overuse of fluorochinolons has higher and age dependent lethality rate.