Children and adolescents with bipolar disorder may have depression as the presenting mood state. It is important for clinicians to distinguish between unipolar and bipolar depression in youth. Depressive episodes are common during the course of bipolar illness in children and adolescents. Evidence-based treatments are needed to guide clinicians' treatment decisions for youth with bipolar depression. This article reviews the prevalence, diagnosis, course, and treatment of bipolar depression in youth, and emphasizes the need for large, controlled treatment studies in the pediatric population.