Fourteen children with adenoid and tonsillar hyperplasia were studied for one night in the sleep laboratory. Six of the children had at least 40 apneic episodes per night, mostly central or obstructive. The largest number of episodes was found in rapid eye movement sleep. Mixed episodes were the longest and central episodes the shortest. Adenotonsillectomy was performed on children with at least 40 episodes and on children with predominantly obstructive episodes. In two of these children, preoperative and postoperative recordings were taken, revealing a reduction in the total number of apneic episodes and a complete disappearance of obstructive episodes. These results suggest that polysomnographic recordings can provide useful information regarding the necessity of adenotonsillectomy.