This article reviews delayed and advanced sleep-wake phase disorders. Diagnostic procedures include a clinical interview to verify the misalignment of the major nocturnal sleep episode relative to the desired and social-normed timing of sleep, a 3-month or greater duration of the sleep-wake disturbance, and at least a week of sleep diary data consistent with the sleep timing complaint. Treatment options include gradual, daily shifting of the sleep schedule (chronotherapy); shifting circadian phase with properly timed light exposure (phototherapy); or melatonin administration. Future directions are discussed to conclude the article.