The auditory brain-stem evoked potential (ABEP) was recorded from 9 female subjects during 1 night of natural sleep. Monaural click stimuli were delivered at a rate of either 11, 41 or 81/sec through a hearing-aid device. The intensity was held constant at 70 dB nHL. In other runs, the intensity was lowered to either 50, 30 or 10 dB, the rate of click presentation being held constant at 81/sec. Tympanic temperature was monitored throughout the recording session. The ABEP was unaltered during any stage of sleep regardless of the rate of presentation or stimulus intensity. Distinct peak V responses were recognizable to within 10 dB of the adult threshold in the sleeping subject. It may be concluded that sleep has virtually no effect on ABEP morphology.