Substance use disorders (SUDs) are highly comorbid with posttraumatic stress disor- der (PTSD). The relationship between substance abuse and trauma is complex and bidirectional, with shared social risk factors and biological pathways. Youth with cooc- curring PTSD and SUD often have more severe challenges than teens with either dis- order alone, with treatment needs that may involve multiple community systems. Integrated treatment principles and recommendations are discussed. Two clinical cases are reviewed to illustrate these treatment principles.