Two cases of Pseudomembranous Colitis are presented in old aged people with multi-systematic failure (renal, respiratory, cardiac) doing mention of favorable circumstances, of the clinic, of the physiopathological hypothesis of the diagnostic and therapeutical ways. They get to the conclusion of the easiness of the development in old people because of their precarious "vascularization" and the need of a systematic study of diarrhea in advanced ages, even though the picture seems simple.