Background: This is a 6-year retrospective quality control study of the LASSO Program (Low Threshold Substitution Treatment in Oslo), using exclusively Suboxone® (buprenorphine-naloxone [BPNX]) in out-patient settings. Adequate abstinence prior to induction is necessary to avoid acute onset opioid withdrawal symptoms; thus, its use in low threshold settings is far less common than methadone. Objectives: The aim of this study was to determine if BPNX is a safe and feasible medication to use in a low threshold setting. Methods: The analysis is based on daily supervised BPNX medication. The standardized induction regime started with 4-mg BPNX increasing by 4 mg daily until 16 mg, with individual adjustments based on clinical status. Treatment effect was evaluated by the number of medication induction attempts, treatment length and lag time between initial contact and medication start. Statistical computations were performed with SPSS®. Results: There were 331 out of 394 registered patient inquires that started on BPNX. Two hundred fifty-three patients (76.4%) completed induction on first attempt with 95% Wilson score CIs of (0.716–0.807). The accumulated percentage increased to 85.2% during successive inductions. No significant association was found between lag time and (i) the number of days on medication during the first induction; or (ii) total treatment length. Patients had a median lag time of 5 days, remained in treatment a median of 52.0 days with an average of 3.9 inductions. There were no cases of severe precipitated withdrawal and only 2 cases of adverse reactions among the 1,293 inductions and 25,544 administered dosages. Conclusion: This study shows that BPNX is highly effective in treating marginalized heroin addicts in low threshold settings. Even during their first attempt, 76.4% completed induction. There were no cases of severe precipitated withdrawal. Prolonged lag time affected neither the length of first treatment nor the total treatment length. Individualized induction readiness approach and motivation were central to the above results.