Anxiety and depressive disorders are highly prevalent, but fewer than half of those who meet diagnostic criteria seek treatment each year. Internet-delivered cognitive behavioral therapy (iCBT) may improve access to evidence-based psychological treatment for people with these conditions. This clinical synthesis focuses on structured iCBT delivered over a period of several weeks or months. Results of meta-analyses consistently indicate the efficacy of therapist-guided iCBT interventions relative to control conditions. This synthesis considers key issues in this rapidly evolving field. Notwithstanding the challenges of safely integrating iCBT into existing mental health services and systems, the authors recommend iCBT interventions as a promising strategy for reaching and treating people with anxiety and depression who might not otherwise receive treatment.