In children and adolescents there have been only few reports dealing with Obstructive Sleep Apnea (OSA) associated with morbid obesity. We report here on sleep-associated breathing disorders in morbidly obese children and the effect of adenoidectomy and tonsillectomy on sleep-associated breathing disorders. The subjects were 31 children with morbid obesity. The mean patient age was 7.9 years ranging from 2 to 14 years. The percentage of expected body weight ranged from 130% to 260%. All of them had adeno-tonsillar hypertrophy. We undertook the study during the period of natural sleep. Percentage of sleeping period with irregular breathing was determined by means of respisomnogram and the percentage of sleeping period with SpO(2) > or = 90% with a pulse oximeter. The percentage of sleeping period with irregular breathing ranged from 10% to 85% before the operation. In all cases, the irregular breathing period decreased almost to zero after the adenoidectomy and tonsillectomy. The percentage of sleeping period with SpO(2) > or = 90% ranged from 1.7% to 95%. The percentage was related to reduction of body weight and it increased gradually as a result of a diet given as therapy. Our studies reveal that weight control may result in partial cure of sleep-associated breathing disorders. Operations, such as adenoidectomy and tonsillectomy, were remarkably effective in treating sleep-associated breathing disorders of severely obese children with large adenoids and tonsils, even if the severe obesity remained.