OBJECTIVES: To describe the utilization pattern of narcotic analgesics and estimate the incidence of suspected addiction treatment among occupational injury cases. METHODS: An analysis of a state-based Worker’s Compensation claims data captured prescription reimbursement information of all injuries that occurred between January 1, 2001 and December 31, 2001. Payment information was followed over a 24-month period following date of injury. A prescription sequence analysis was carried out to estimate treatment incidence rates of potential addiction due to narcotic analgesic use. RESULTS: Of the 48,598 occupational injury cases, about 10% (N = 4,644) received at least 1 narcotic analgesic (therapeutic class H3A). Average length of therapy was 183 days, with 40% of patients receiving narcotic analgesics for greater than 120 days. The majority of narcotic prescriptions were for hydrocodone (55%). Nine percent of patients received less than four different types of narcotic analgesics. From the prescription sequence analysis, we identified 65 cases who received either methadone or clonidine, medications indicated for addiction treatment or detoxification. The incidence rate of receiving treatment for narcotic withdrawal or detoxification was 14 per 1000 patients on narcotic analgesic therapy (95% CI: 10.6, 17.4). Among patients who received potential detoxification treatment, the median duration from initiation of narcotic analgesic therapy to need for withdrawal or detoxification therapy was 232 days. A Cox Proportional Hazards model identified greater risk of suspected methadone use in oxycontin treated patients compared to other narcotic treated patients (P < .01). CONCLUSIONS: To our knowledge, this is the first study that estimated the incidence rates of suspected addiction treatment due to narcotic analgesics used in the Worker’s Compensation population using sequential prescription analysis. The study has implications for developing strategies to manage narcotic analgesic prescribing practices and reduce the risk of addiction among injured workers who are narcotic analgesic users.