The self-selection factor is pervasive in health care and is assumed to be a contributor to achieving therapeutic goals. For example, the therapeutic efficacies of medications or mental health approaches are assessed with those individuals who undergo or use the therapy. In addiction treatment research, however, self-selection is viewed as a methodological problem. The conventional criticism of evaluative research is that self-selection undermines conclusions concerning the efficacy of addiction treatment. This commentary reconsiders the issue of self-selection in addiction treatment within the context of clinical experience, developing theory, and research on motivation and recovery stages. A new perspective is outlined that redefines the importance of self-selection in interpreting the effectiveness of treatment. Implications are discussed for research design, treatment policy, and treatment practice.