Background: Opioid use is a serious global problem and the problem is increasing over years. Buprenorphine has been approved as a substitution therapy in Nepal, but there are few long-term studies of its effectiveness. Aim: This study aimed to assess the 1-year efficacy of buprenorphine and reasons for dropout. Materials and Methods: This study was conducted at Western Regional Hospital, Pokhara from 29th August 2016 to 31st August 2017. The Buprenorphine Maintenance Treatment Program (BMT) was started on 29th August 2016 and all the clients enrolled in the program within 1 year of starting BMT were included in the study. Results: 75% of the enrolled clients dropped out in 1-year period. Conclusion: Adherence to Buprenorphine was better in flexible dose adjustment group. Combination of buprenorphine and psychosocial treatment would have been related with better outcome.