Irritable bowel syndrome (IBS) is a functional disorder characterized by chronic or recurrent abdominal pain or discomfort with bowel disturbances. This prospective, randomized clinical trial has been conducted on IBS patients, using trimebutine and Mebeverine in separate group in parallel design to compare the efficacy and safety of Trimebutine 100mg twice daily with mebeverine 135mg twice daily. Patients of 15 to 60 years old and both sexes were included from the out patient department (OPD) of gastroenterology, Bangabandhu Sheikh Mujib Medical University (BSMMU) from June 2010 to December 2011. A validated IBS-QOL instrument consisted of 34 questions used to assess improvement of quality of life before and after treatment. A total of 140 patients were enrolled in this study. Eighteen patients dropped out. One hundred twenty two patients completed the trial. In this study at the end of 6 weeks therapy, improvement of symptoms was statistically significant. However, differences of improvement between the two groups in relieving various symptoms were not statistically significant. Mean QOL score before treatment was 103 in Trimebutine group and 106 in Mebeverine group. After 6 weeks of treatment mean QOL score was 82 in Trimebutine group and 95 in Mebeverine group indicating improvement in both groups was statistically significant. The difference between the two groups was also significant. No worsening of symptoms and no side effects of the therapeutic agents was observed in any patient during the trial.