We investigated the properties of small cells in the vomeronasal sensory epithelium of adult rats. The sensory neurons in the sensory epithelium were stained by antibodies to G(i2alpha) and G(oalpha) in their cell bodies and dendrites, while the small cells, which formed a cluster in the epithelium, were not stained at all. Voltage-activated inward currents were not detected by patch-clamp recordings, but outward currents were induced by the application of voltage step pulses. These results suggest that the small cells are different from the vomeronasal sensory neurons. Bromodeoxyuridine (BrdU) labeling indicated that dividing cells existed in the cluster of small cells.