The properties of the olfactory bulb potential evoked by electrical stimulation of the olfactory mucosa were studied in rabbits immobilized with d-tubocurarine. The evoked potential was a slow negative wave when recorded from the surface of the bulb. In favorable conditions, the falling phase of the main deflection carried the second negative wave which was readily suppressed by barbiturate anesthesia and by the centrifugal impulses. The evoked potential reversed in polarity when the recording microelectrode was inserted in the deep layer. During high frequency stimulation of the anterior commissure the evoked potential was completely inhibited. The potential was suppressed by local application of gamma aminobutyric acid, Studying the unitary activity, it was observed that olfactory mucosa stimulation caused not only excitation but also inhibition of the single neuron discharge. These findings were discussed in relation to the histological structure of the olfactory bulb.