Increasing rates of Clostridium difficile-associated diarrhoea (CDAD) with an unusual, severe course have been reported in Canada, USA and several European countries since 2003. A new virulent strain, PCR ribotype 027 (CD027), is associated with this increase. We report the first Danish case of CDAD caused by CD027. A 85-year-old woman was admitted to hospital with pneumonia. Following treatment initially with penicillin, secondly with moxifloxacin she developed bloody diarrhoea. A stool specimen showed CD027. She was treated with metronidazol for ten days and recovered completely.