Insomnia in the pediatric populations is very different than insomnia in the adult population. Although both involve sleeplessness, the causes vary significantly. Sleeplessness during early infancy is normal, and the developing sleep-wake pattern of an infant is inconsistent with the normal sleep-wake pattern of parents. Asynchrony of parental and infant sleep patterns can lead to specific complaints of sleeplessness in infants. Parental response to the infant's developing sleep-wake pattern may be a factor that determines the presence (or absence) of problem sleeplessness as the child matures. Problem sleeplessness in children may result from behavioral, circadian, or biologic or medical abnormalities. Therefore, evaluation of the sleepless child should not be limited to only behavioral etiologies.