OBJECTIVES: To assess the health care utilization and associated costs for osteoarthritis (OA) patients, depending on the primary drug prescribed for pain management. METHODS: A claims database of privately insured patients (covering 31 employers, 1999-2004) was used to identify OA patients (ICD-9-CM 715.XX) OA patients were categorized by primary pain drug treatment – defined as greatest days supply, 2003-2004 – for pain management (tramadol, acetaminophen w/codeine, Cox-IIs, NSAIDS, short-acting opioids). A tramadol monotherapy cohort was also constructed in which patients were prescribed only tramadol for their pain (i.e., these patients did not receive any of the other primary pain drugs listed above.) Mean annual per patient health care costs were calculated for each drug treatment cohort from a private payer's perspective. RESULTS: OA patients (n=32,043) were often prescribed multiple drugs simultaneously and/or sequentially to manage pain. Average annual direct medical costs for OA patients were $8,602 (ranging from $6,011 to $13,964 depending on the drug treatment cohort). Average annual drug costs for OA patients were $2,941 (ranging from $2,108 to $8,498 depending on the drug treatment cohort). The tramadol monotherapy cohort had lower costs than other cohorts. Cohort cost differences reflect, in part, more severe comorbidity profile and complex temporal treatment patterns. CONCLUSION: Average annual direct costs of OA patients were $11,543, which varies by drug treatment cohort. OA patients use multiple simultaneously and/or sequentially to treat their pain. Prescribing tramadol earlier to treat OA may reduce therapy switching and associated costs and a once-a-day version of tramadol may offer additional convenience, tolerability and sleep improvement benefits for OA patients. Future research is needed to identify the temporal patterns of tramadol use and associated outcomes.