Auditory arousal thresholds were determined throughout sleep (4-night protocol) in prepubertal nonmedicated and medicated hyperkinetic and normal control male children. The most striking result was the general inability to arouse children of all groups to behavioral response even at intensities up to 123 dB sound pressure level. Of total awakening attempts, 52.5% resulted in non-arousal, 13% resulted in partial, nonsustained physiological arousal responses, and 34.3% were associated with complete awakenings. A significant increase in proportion of awakenings and decrease in the frequency of nonarousals occurred across the night. The groups did not differ with respect to the number of arousal responses. Although nonmedicated hyperkinetic children tended to have lower arousal thresholds relative to children in both comparison groups, the only significant group difference was a lower threshold response in nonmedicated, relative to medicated, hyperkinetic subjects during stage 2 sleep. Arousal thresholds in hyperkinetic children receiving stimulant medication approximated those of normal control children. The enhanced sensitivity of nonmedicated hyperkinetic subjects to auditory stimuli during sleep is interpreted as indicating that processes responsible for elevating arousal threshold at this time are less effective in these children.