Smith-Magenis syndrome (SMS) is a rare (1/25,000) clinically recognizable syndrome, characterized by the following features: a distinct pattern of minor craniofacial and skeletal anomalies, expressive speech/language delays, psychomotor and growth retardation, and a striking neurobehavioral phenotype. This phenotype includes stereotypies, self-injurious and aggressive behaviors, and a chronic sleep disorder associated with an inverted circadian melatonin rhythm. Sleep disturbances include daytime sleepiness, early sleep onset, and early morning awakening. Disturbed sleep is the strongest predictor of maladaptive behavior in children with SMS. Diminished nocturnal sleep is virtually universal in SMS, representing a major challenge to the patient and family. The majority (greater than 95%) of cases are due to interstitial deletion of 17p11.2; however, rare cases due to RAI1 gene mutations are also reported.