Bedtime struggles, delayed sleep onset, and problematic night wakings are extremely common in the pediatric population, and have a significant impact on quality of life of both children and caregivers. This article reviews the research and clinical nosology of childhood insomnia, prevalence, and etiologic factors in infants, children, and adolescents. Clinical presentation, evaluation, and treatment, both behavioral and pharmacologic, of the most common types of pediatric insomnia are presented. Insomnia in special populations, particularly children with chronic medical, psychiatric, and neurodevelopmental disorders, is discussed. Future directions in childhood insomnia are presented.