OBJECTIVES: Chronic pain is a major public health concern in the US.  Established guidelines are available for management of non-malignant chronic pain, including opioid use.  However, discrepancies in opioid prescribing patterns due to physician misconceptions remain concerning. Therefore, this study evaluated pain medication use and investigated determinants of opioid analgesic prescribing in the US outpatient settings for common non-malignant chronic pain indications. METHODS: This cross-sectional study analyzed the National Ambulatory Medical Care Survey(NAMCS) data from 2002-2007 on patients 18 years and older with non-malignant chronic pain diagnosis based on ICD-9-CM codes identified as reason for visits.  Pain medications prescribed were retrieved using NAMCS drug codes.  Multivariate logistic models examined determinants of opioid prescribing among chronic pain patients.  RESULTS: Approximately 69 million weighted outpatient visits were reported for non-malignant chronic pain between 2000-2007 in the US.  The mean age for patients was 53 (range 18-100) and the majority were women(63%).  Neuropathic pain was reported for 2.39% visits while 16.24% had an inflammatory pain diagnosis.  Non-medication treatment was prescribed during 26% of these visits.  While most(95%) visits reported prescribing NSAIDs, 29% reported receiving prescriptions for more than five medications.  Primary care physicians (PCPs) were 1.74 times more likely to prescribe opioids [OR(odds ratio):1.74, CI:1.42-2.14] than other specialty physicians.  Patients receiving more than five medications were 2.80 times more likely to receive opioids (OR:2.80,CI:2.28-3.44) than those with less than five medications.  Patients from the southern region of the US were 1.43 times more likely to receive opioids (OR:1.43,CI:1.06-1.94) than patients from the northeast region. CONCLUSIONS: According to our study, visits with PCPs, more than five prescriptions, established patients, and physician visits in the southern region of the US were some of the determinants of opioid prescribing.  Increased awareness of opioid prescription guidelines for pain management may eliminate prescription discrepancies and improve patient care.