This Practice Parameter reviews the evidence from research and clinical experience and highlights significant advances in the assessment and treatment of posttraumatic stress disorder since the previous Parameter was published in 1998. It highlights the importance of early identification of posttraumatic stress disorder, the importance of gathering information from parents and children, and the assessment and treatment of comorbid disorders. It presents evidence to support trauma-focused psychotherapy, medications, and a combination of interventions in a multimodal approach.