The objectives of this article are, first, to provide a brief review of screening and assessment of adolescents substance use and substance use disorders; second, to describe the work done with the Teen Addiction Severity Index (T-ASI) in different countries; and third, to address challenges and opportunities in order to improve international collaboration between health professionals responsible for providing substance abuse services for youth and families. It is recommended that the International Society of Addiction Medicine (ISAM) sponsor and coordinate the efforts to disseminate the benefits accrued from already developed assessment and treatment of substance use disorders of youth into different countries and regions. Addiction professionals representing a myriad of cultures, ethnic, and racial groups would be encouraged to translate the assessments into relevant languages and dialects and with the support of the original authors conduct reverse translation and then test the psychometric properties before a wider use commences. (Contains 2 tables.)