BACKGROUND: There is controversy about which outcome parameters should be employed to assess substance use treatment. Subjective measures of medication-assisted treatment (MAT) of opioid dependence are increasingly important. However, while patients' perspectives have been examined, the caregivers' views remain largely unknown. Here, we explore how physicians evaluate MAT, and which predictors are most relevant. METHODS: We conducted a retrospective cohort study of all MAT episodes with oral opioid agonists in the canton of Zurich between 1998 and 2013 using a case register. Termination forms of the register include a physician-completed assessment on the course of the treatment episode. Mixed model analysis was applied to determine relevant predictors. RESULTS: The analysis was based on 17,234 episodes from 7432 patients. Mean global assessment of the course of MAT was 'moderate'. The most important predictors for treatment evaluation by physicians were treatment break off as reason for termination (p<0.0001), psychological improvement throughout treatment (p<0.0001), wish for abstinence from the substitute (p<0.0001), social integration index at termination (p<0.0001), and social (p<0.0001) as well as medical (p<0.0001) improvement. The negative association of treatment break off with MAT assessment was more pronounced in semi-rural than urban areas (p<0.0001). CONCLUSION: Predictors relating to the well-being and functioning of the patient as well as the reasons underlying treatment termination appear to be more important for the treating physician's evaluation of medication-assisted treatment episodes than on-going substance use. Coming off the opioid medication plays a central role, independent of ongoing illicit substance use. Predictors relating to the well-being and functioning of the patient as well as the reasons underlying treatment termination appear to be more important for the treating physician's evaluation of medication-assisted treatment episodes than on-going substance use. Coming off the opioid medication plays a central role, independent of ongoing illicit substance use.