 Various studies have been conducted in past using different strains of probiotics in evaluating IBS symptoms. The results are by no means consistent and the overall impact of probiotics in IBS remains unclear. However, recently OMahony L et al have shown that Bifidobacterium infantis 35624 alleviates symptoms in IBS; this symptomatic response was associated with normalization of the ratio of an anti-inflammatory to a proinflammatory cytokine IL-10IL-12 ratio, suggesting an immune-modulating role for this organism, in this disorder.Saccharomyces boulardii is a probiotic yeast that has been successfully used for the antibiotic induced diarrhea, prevent relapse of Clostridium difficile and Crohns disease. It ameliorates intestinal injury and inflammation caused by a wide variety of enteric pathogens.We therefore plan a Double-blind, randomized, placebo-controlled study to assess the effects of Saccharomyces boulardii in improving symptomatology of diarrhea predominant IBS and its effect on quality of life. We also plan to assess the changes in the relative production of anti-inflammatory interleukin IL-10 to proinflammatory cytokines IL-12, IL-8 and TNFα. 