This course is the first three chapters of SAMHSA's Substance Use Disorder Treatment for People With Co-Occurring Disorders, Treatment Improvement Protocol (TIP) Series, No. 42. Presented is the reason for this protocol, the need for knowledge of substance use disorder as it relates to those with other co-occurring disorders, and the proper screening and assessment of these patients. The course explains the guiding principles in dealing with such patients and the principals of treatment, assessments, and healthcare providers competencies. Included are the protocol for proper screening and assessment of this patient population. There is also a multiple step assessment tool for the healthcare professional.