Suicide is the third leading cause of death among young people in the U.S. and represents a significant public health problem worldwide. This review focuses on recent developments in our understanding of the epidemiology and risk factors for adolescent suicide and suicidal behavior. The suicide rate among children and adolescents in the U.S. has increased dramatically in recent years and has been accompanied by substantial changes in the leading methods of youth suicide, especially among young girls. Much work is currently underway to elucidate the relationships between psychopathology, substance use, child abuse, bullying, internet use, and youth suicidal behavior. Recent evidence also suggests sex-specific and moderating roles of sex in influencing risk for suicide and suicidal behavior. Empirical research into the causal mechanisms underlying youth suicide and suicidal behavior is needed to inform early identification and prevention efforts.