Infectious diarrhoea in the elderly is associated with high morbidity and mortality and need early diagnosis and treatment. Polypathology, malnutrition, polytherapy, length of stay in the hospital and residence in nursing-home contribute to the increasing incidence and gravity of these diseases with aging. Viral gastroenteritis is responsible for epidemic in nursing-home residents. Bacterial gastrointestinal infections are primarily caused by enterotoxigenic agents inducing sporadic or epidemic infections food poisoning. Older adults are more particularly exposed to antibiotic-associated diarrhoea. Clostridium difficle has been increasingly recognized as a cause of pseudomembranous colitis in elderly and is associated with increased mortality. The approach to an old patient with suspected infectious diarrhoea should be to eliminate the likely noninfectious causes, to detect immediate complications due to hydroelectrolytic loss, to initiate early appropriated oral rehydration therapy so as to prevent dehydratation, to avoid the use of antimotility drugs, and to evaluate and to take over nutritional consequences of diarrhoea.