Two identical, randomized, phase 3 trials conducted over a 3-month period. A total of 1258 patients meeting Rome II criteria for IBS received XIFAXAN 550 mg 3 times a day (n=624) or placebo (n=634) for 14 days. Primary endpoint was adequate relief of IBS signs and symptoms for at least 2 of 4 weeks during the month following 14 days of treatment. Adequate relief was defined as a response of “yes” to the weekly Subject Global Assessment (SGA) question: “In regards to your IBS symptoms, compared to the way you felt before you started study medication, have you, in the past 7 days, had adequate relief of your IBS symptoms? [Yes/No].” Primary endpoint: 41% of patients (254 of 624) in the XIFAXAN 550 mg group, 31% of TARGET 1 placebo group (98 of 314) and 32% of TARGET 2 placebo group (103 of 320) experienced adequate relief of IBS signs and symptoms. Composite endpoint was defined as ≥30% decrease from baseline in abdominal pain with a weekly average stool consistency score of <4 (loose stool) for ≥2 weeks during the month following 2 weeks of treatment. Composite endpoint: 47% of patients (291 of 624) in the XIFAXAN 550 mg group, 39% of TARGET 1 placebo group (121 of 314) and 36% of TARGET 2 placebo group (116 of 320) experienced symptom improvement based on the composite endpoint.