Community studies have shown that stressful life events, psychological distress, and depressive and anxiety disorders are associated with 1) a range of medical symptoms without identified pathology, 2) increased health care utilization, and 3) increased costs. In both primary care and medical specialty samples, patients who have syndromes with ill-defined pathologic mechanisms (such as the irritable bowel syndrome and fibromyalgia) have been shown to have significantly higher rates of anxiety and depressive disorders than do patients with comparable, well-defined medical diseases and similar symptoms. Other studies show that after adjustment for severity of medical illness, patients with depression or anxiety and comorbid medical disease have significantly more medical symptoms without identified pathology than do patients with a similar medical disease alone. Both childhood maltreatment and psychological trauma in adulthood have been associated with increased vulnerability to psychiatric illness and more medical symptoms. The substantial functional impairment, distress, and costs associated with medical symptoms without identified pathology suggest that research studies promoting a better understanding of the biopsychosocial cause of these symptoms may yield pragmatic, cost-effective approaches to treatment in medical settings.