For this study, sleep EEG of eleven healthy adult subjects ranged from 25 to 30 years of age were observed during stage 3 and evoked K-complex and AEP were both concordantly recorded to investigate the correlation between latencies of s-components in the K-complexes and N4-components in the AEPs during stage 3. The results obtained were as follow: (1) Three distinct components of K-complex such as sharp wave, slow wave (s-component) and burst wave of 12-14 c/sec were found almost constantly during stage 3. (2) It can be concluded that the evoked K-complexes (s-components) in the EEG were almost equivalent to the AEPs (N4-components) if both were concordantly recorded time-locked to click stimuli which were presented every 10 sec with 15 decibels during stage 3. (3) S-component of K-complex such as slow wave was attributed to the impulse bombardment of the nucleus reticularis thalami which is a frequency gate following the hypothesis of Scheibel, M.E. and Scheibel, A.B..