Functional disturbances occur in approximately 10% to 15% of the general population and in a similar percentage of patients with inflammatory bowel disease (IBD). Because overlapping irritable bowel syndrome (IBS) is so common, one of the most important interventions a clinician can make is recognizing its existence. This requires a thorough understanding of underlying pathophysiologic processes. Differentiating among the causes of symptoms is especially significant in a minority of patients mislabeled as having 'refractory IBD.' Escalating therapy directed at disease activity may have no effect on functional symptoms other than to reinforce their presence. Treatment of IBS in patients with IBD is similar to that of the general population. The cornerstone of treatment is establishing a constructive doctor-patient relationship. Initial therapy usually involves a conservative approach that includes patient education and diet and lifestyle modifications. Pharmacologic treatment is individualized and generally directed at the predominant symptoms. Options may broadly include antispasmodics, antidiarrheals, and antidepressants, either alone or in combination. Psychosocial therapies have shown to be beneficial in selected individuals.