The pathogenic role of certain microorganism of intestinal flora has been demonstrated in experimental colitis in animals and strongly suspected in inflammatory bowel disease in human, especially in Crohn's disease and pouchitis. Probiotics are living non pathogenic microorganisms that, upon oral ingestion exert benefits on human health by modulating enteric flora or by stimulation of local immune system. The aim of this article is to remind the role of intestinal flora in inflammatory bowel disease, the mechanism of inflammation induced by this flora and to review through the literature, the different clinical studies performed with probiotics in human.