Gi2 alpha and G(o) alpha proteins were immunohistochemically localized, respectively, to the rostral and caudal accessory olfactory bulb of Brazilian opossums. In the vomeronasal organ, Gi2 alpha- and G(o) alpha-immunoreactive neurons were located in the middle and basal layers, respectively, of the sensory epithelium. Both G protein antibodies stained the microvillar surface of the epithelium and the nerve bundles in the subepithelial mucosa.