BACKGROUND: Opioids have been linked to increased risk of fractures, but little is known about how opioid dose affects fracture risk. OBJECTIVE: To assess whether risk of fracture increases with opioid dose among older patients initiating sustained use of opioids for chronic non-cancer pain. DESIGN: A cohort study that uses Cox proportional hazards models to compare fracture risk among current opioid users vs. persons no longer using opioids. PARTICIPANTS: Members of an integrated health care plan (N = 2,341) age 60 years and older who received 3+ opioid prescriptions within a 90-day period for chronic, non-cancer pain between 2000 and 2005. MEASUREMENTS: Time-varying measures of opioid use and average daily dose in morphine equivalents were calculated from automated data. Fractures were identified from automated data and then validated through medical record review. RESULTS: Compared with persons not currently using opioids, opioid use was associated with a trend towards increased fracture risk (1.28 (95% CI (0.99, 1.64 )). Higher dose opioid use (>or=50 mg/day) was associated with a 9.95% annual fracture rate and a twofold increase in fracture risk (2.00 (95% CI (1.24, 3.24)). Of the fractures in the study cohort, 34% were of the hip or pelvis, and 37% were associated with inpatient care. CONCLUSIONS: Higher doses (>or=50 mg/day) of opioids for chronic non-cancer pain were associated with a 2.00 increase in risk of fracture confirmed by medical record review. Clinicians should consider fracture risk when prescribing higher-dose opioid therapy for older adults.