Pain is the most common symptom reported in both the general population and the general medical setting (Kroenke 2003b; Sternbach 1986; Verhaak et al. 1998). Pain complaints account for more than 40% of all symptom-related outpatient visits, or over 100 million ambulatory encounters in the United States alone each year (Schappert 1992). Pain costs the United States more than $100 billion each year in health care and lost productivity (Stewart et al. 2003). Pain medications are the second most commonly prescribed class of drugs (after cardiac-renal drugs), accounting for 12% of all medications prescribed during ambulatory office visits in the United States (Turk 2002). Yet nonopioid analgesics fail to provide adequate relief in many patients (Curatolo and Bogduk 2001), and physicians' concerns about regulatory restrictions as well as risks of tolerance or addiction constrain the prescribing of opioid analgesics for noncancer pain (Joranson et al. 2002). Moreover, opioids themselves may produce only moderate reductions in chronic pain (Furlan et al. 2006; Martell et al. 2007; Turk 2002) and may fail to improve (or may even worsen) psychological outcomes (e.g., depression) or functional status even when they do alleviate the pain (Moulin et al. 1996). At the same time, clinicians are being pressured to respond to pain as the "fifth vital sign" (Joint Commission on Accreditation of Healthcare Organizations 2000). In House Resolution 1863, the National Pain Care Policy Act of 2003, Congress declared this the "Decade of Pain Control and Research." Indeed, persistent pain is a major international health problem (Gureje et al. 1998), prompting the World Health Organization to endorse a global campaign against pain (Breivik 2002). Persistent pain may lead to excessive surgery or other expensive or invasive procedures and is the leading reason for use of complementary and alternative medicine (CAM) (Astin 1998). Pain is also among the most common reasons for temporary as well as permanent work disability (B. H. Smith et al. 2001). Many pain treatment recommendations are based principally on expert consensus rather than on clinical trial results (Bair et al. 2005) and have yet to influence primary care practice (Chodosh et al. 2001).