The Science of Co-occurring Disorders training program offers a unique experience in transdisciplinary research related to the co-existence of substance use and other mental disorders. Six interconnected groups provide research opportunities in social, behavioral, and neurobiological mechanisms, treatment development (psychosocial and pharmacological), technology-assisted treatment and dissemination, and health services practices and implementation. This dynamic, mentor-oriented training program accommodates 4 post-doctoral and 3 pre-doctoral positions.