The relationship between the EEG topography and sleepiness was investigated in 5 normal students (aged 21- 26 yrs). They were assessed their sleepiness for 12 hours (19:00 to 07:00) at 20 min intervals via Kwansei-Gakuin sleepiness scale (KSS), visual analog scale (VAS) and the multiple sleep latency test (MSLT). The power spectra derived from 16 EEG leads were topographically displayed for every 1 Hz from 8 to 13 Hz, based on the initial 30 s EEG recordings of each MSLT period. With increasing sleepiness, the slow alpha band activities (8-9 Hz) developed around the occipital area, while the fast alpha band activities (12-13 Hz) tended to obscure at the parietal area. The topographic pattern for the activities of intermediate alpha band (10-11 Hz) were unchanged over the experimental period. These data suggest that the increase or decrease of the amplitude of the slow alpha activity and the fast alpha activity reflect the variation of sleepiness. The present study supplied the new perspectives for the study of sleepiness in terms of topographic mapping of the waking EEG.