The pathogenesis of inflammatory bowel disease (IBD) involves an interaction between genetically determined host susceptibility, dysregulated immune response, and the enteric microbiota. Ecological treatments including probiotics, prebiotics, and synbiotics are actively studied in Crohn's disease (CD), ulcerative colitis (UC) and pouchitis. We review herein the literature on the rational use of probiotics in IBD considering efficacy (as evaluated in randomized controlled trials), mechanisms of action and safety issues. A probiotic effect is strictly restricted to one defined strain and cannot be generalized from one to another. There is evidence of efficacy of some probiotic drugs in pouchitis (VSL#3), and in the prevention of recurrence of UC (Escherichia coli Nissle 1917). However, the evidence for efficacy of probiotic drugs in CD is still low as well as that of dietary ecological treatments. Despite an ecological (hopefully nutritional) treatment of IBD is promising, many questions remain unanswered and further clinical and fundamental studies are needed.