61 snoring children selected for adenotonsillectomy, mainly for recurrent tonsillitis, were compared with a matched group of 31 healthy children for symptoms of sleep apnoea, extent of sleep hypoxaemia, and amount of sleep disturbance. The studies were repeated six months postoperatively, and after six months in the healthy children. Preoperatively, 61% of the children had degrees of sleep hypoxaemia above normal and 65% had abnormally disturbed sleep. A questionnaire administered to the parents about their children showed abnormal patterns of answers about sleep problems daytime sleepiness, hyperactivity, aggression, learning difficulties, restless sleep, and odd sleeping positions. After adenotonsillectomy, the abnormal hypoxaemia, excessive sleep disturbance, and multiple symptoms almost resolved; a growth spurt also occurred.