The notion that the intestinal microbiota plays a key role for the development of intestinal inflammation, initially based on a series of clinical observations both in human inflammatory bowel disease and experimental colitis, has been reinforced by a growing body of evidence demonstrating that the abnormal recognition of bacterial and other microbiota antigens by the innate immune system is one of the earliest events in the pathogenesis of inflammatory bowel disease. In keeping with our present knowledge of inflammatory bowel disease pathophysiology, the search for therapeutic approaches aimed at modifying the composition of the intestinal microbiota to obtain new, more targeted treatments for inflammatory bowel disease that are basically free of side effects has been a subject of intense research activity. Probiotics are defined as live organisms capable of conferring health benefits beyond their nutritional properties. Numerous micro-organisms have been evaluated to induce or maintain remission, or both, in ulcerative colitis, Crohn's disease and pouchitis. Overall, probiotics have successfully demonstrated some efficacy in some inflammatory bowel disease scenarios. However, a critical review of the available scientific literature shows that: (1) in spite of great expectations, reflected by a high number of review and editorial articles in top journals, the number of published, well-designed clinical trials using probiotics in inflammatory bowel disease is small, often with few patients; (2) the range of microbial agents makes it particularly difficult to draw global conclusions; (3) the quality of the evidence on the efficacy of probiotics in pouchitis is clearly better than that in ulcerative colitis, while there is virtually no evidence of probiotic efficacy in Crohn's disease. The appropriate selection of probiotic agents combined with convincing clinical trials will determine whether probiotics can jump from promise to reality in inflammatory bowel disease clinical practice.