OBJECTIVE:: To compare rates of hospital and emergency department (ED) attendance in opiate-dependent patients treated implant naltrexone, with patients treated with methadone and buprenorphine. MATERIALS AND METHODS:: Treatment records for opiate-dependent patients treated with implant naltrexone, methadone, or buprenorphine were linked with routine, prospectively collected health data sets. Rates of hospital and ED attendances were calculated for each cohort and compared using generalized estimating equations. RESULTS:: Following the commencement of treatment, rates of hospitalizations was significantly higher in patients treated with implant naltrexone compared with both methadone [risk ratio (RR), 0.83, confidence interval (CI), 0.77-0.89] and buprenorphine (RR, 0.92, CI, 0.85-0.99), as were rates of ED attendances in methadone-treated patients (RR, 0.85, CI, 0.78-0.92), whereas rates of ED attendances in buprenorphine patients were comparable (RR, 0.92, CI, 0.85-1.01). The difference was largely attributable to the induction period (0 to 28 d), where rates of hospital and ED attendances in naltrexone-treated patients were almost double that of both methadone and buprenorphine. However, after the initial period and following the cessation of treatment, rates of hospital and ED attendances in naltrexone-treated patients were less than or equivalent to methadone or buprenorphine patients. CONCLUSIONS:: Rates of morbidity in opiate-dependent patients treated with implant naltrexone were significantly elevated compared with methadone and buprenorphine in the first 28 days of treatment, however, are comparable after this initial period.