Over the past several years, a number of studies have addressed the role of specific strains of bacteria, or combinations thereof, to alleviate certain symptoms of irritable bowel syndrome (IBS). More importantly, the precise factors that contribute to this therapeutic effect, such as modulations in cytokine levels and alterations in colonic motility, are being clarified. This review serves to summarize the evidence for the use of probiotics in the treatment of IBS and to place this information in clinical context. Potential future developments and areas of possible research are also discussed.