This is a secondary analysis of a randomized, double-blind study comparing 100 mg and 300 mg maintenance doses of extended-release buprenorphine (BUP-XR). All patients (n=311) received 2 monthly induction doses of 300 mg BUP-XR followed by 4 monthly maintenance doses of either 100 mg or 300 mg BUP-XR. For patients who had not been using opioids by injection, there was no difference in weekly abstinence or treatment retention comparing the two maintenance doses. However, for patients with a history of injecting opioids, the 300 mg maintenance dose resulted in significantly higher percentages of weeks abstinent as well as improved treatment retention. The authors speculated that opioid injecting patients may have had higher levels of tolerance that required a higher maintenance dose.