This guide, published by SAMHSA, intends to educate clinicians and other stakeholders about the harms of using more than one substance and consideration for addressing concurrent substance use and concurrent substance use disorders. The guide provides considerations and strategies for clinicians and organizations implementing evidence-based practices. These approaches will assist clinicians, behavioral health organizations, primary care providers, insurers, and policy makers in understanding, selecting, and implementing evidence-based interventions that support adults with concurrent substance use and/or concurrent substance use disorders. Evidence-based strategies are outlined in this report.