Abstract: The understanding of irritable bowel syndrome (IBS) has undergone a rapid evolution with scientific advancement, but historically it was recognized over 150 years ago. IBS is a common functional bowel disorder that generates a significant health care burden. The percentage of patients seeking health care related to IBS approaches 12% in primary care practices and is by far the largest subgroup seen in gastroenterology clinics. It has been well documented that these patients exhibit a poorer quality of life and irritable bowel syndrome laze the health care system to a greater degree than patients without this diagnosis. The majority of these patients will never seek medical care. For etiology and pathogenesis basis altered gastrointestinal motility, visceral hypersensitivity, post infectious reactivity, brain–gut interactions, alteration in fecal microflora, bacterial overgrowth, food sensitivity, carbohydrate mal absorption, and intestinal inflammation all have been implicated in the pathogenesis of IBS. 11-point questioner is most recent Rome III criteria to allow for ease of diagnosis. Abdominal pain, altered bowel habit, flatulence and other symptoms like sense of incomplete excavation and burning pain in epigastrium were presentation in cases. Methods: Single blind placebo-controlled study design has been adopted to know Effectiveness of Homoeopathic medicine Mercurius solubilis in the treatment of irritable bowel syndrome. A total number of 80 patients were involved in study having age group 20 to 60 years, both gender and all socioeconomically classes, who fulfilling the inclusion and exclusion criteria. Test group A-40 cases administered Homoeopathic medicine Mercurius solubilis and Control Group B-40 cases, received Placebo up to Three months with at least six visits. Result: All data was calculated from the study of 80 individuals. Statistical tests regarding the various parameters were conducted and ratio of cure was found out in relation to the medicine used. Conclusion: Hence finally it is concluded that, there is significant difference in result between groups of IBS patients receiving homoeopathic medicine and placebo. Mercurius solubilis is significantly effective than placebo.