Sleep problems are common in childhood. They are reported in about a quarter of young children, usually in the form of settling difficulties or night waking. The types and frequency of sleep disturbance tend to vary with age and, although some remit spontaneously, a substantial proportion of them persist. Particularly high rates of sleep disturbance occur in children who have learning disabilities, are physically ill, or psychologically disturbed. The immediate effects of sleep problems are important but so, also, are the longer-term effects which may influence the child's physical, psychological, and social development. Persistent sleep disturbance is associated with behavioural disturbance in children and may affect performance in school. Raised levels of maternal stress and impairment of parenting skills have also been reported as a consequence.