Adenotonsillar hypertrophy is a well-defined clinical entity which causes snoring and sleep apnea in children. The authors had described in a previous report various methods of evaluating the severity of upper airway obstruction and monitoring the respiratory distress accompanied by adenotonsillar hypertrophy. In this study we analyzed the changes of snoring and sleep apnea after tonsillectomy and adenoidectomy in children who had had snoring and/or sleep apnea preoperatively. Postoperatively, snoring was shown to have been cured or improved in 92%(24/26) of cases, while sleep apnea was improved in 75%(21/28) of cases. This means that tonsillectomy and adenoidectomy is mandatory to relieve the upper airway obstruction caused by adenotonsillar hypertrophy.