The aim of this study was to evaluate the effects of propofol on cortical electroencephalogram (EEG) in seven dogs. Propofol infusion was accomplished from low concentration to high concentration in series, and each concentration was infused for 20 minutes (M0: 0, M0.5: 0.5, M1.0:1.0, and M1.5: 1.5 mg/kg/min of infusion rate). EEG was recorded via needle electrode placed at Cz, which was applied to International 10-20 system. Arterial blood pressure. blood gas analysis and ECG were also measured. Hoemodynamics, Pa$CO_2$, PaO$_2$, heart rate and respiratory rate were variable, but were net significant(p>0.05). The power spectra of EEG in every concentration was compared wish those of control (MO). The powers at a1l frequencies at M1.0 and Ml.5 were decreased. Especially, the powers of the frequencies over 20 Hz were significantly decreased (p<0.O5). Powers at frequencies between 8 and 15Hz at MO.S were significantly increased (p<0.05) in response to the painful stimuli. It was inferred that they may reflect activity of the brain which is consciously processing the external Stimuli. Like the Power spectra, al1 the band powers of He EEG ($delta$ 1-4, $ heta$4-8, $alpha$ 8-13, $eta$L13-21. $eta$H 21-30, ulcorner 30-50, and total 1-5OHz) were decreased in proportion to the increase of infusion rate at M1 .0 and M1.5. Especially, decrease of $eta$H and ${gamma}$ were significant(p<0.01). At M0.5, $alpha$ band was significantly increased(p<0.05) among all the bands. Seizure activities which were concide with occurrence of spike wave were shown in all dogs at Ml .0 and M1.5.