A functional vomeronasal organ is present in most land-living vertebrates, but not in all. Studies in a limited number of mammals have shown that stimulation of the vomeronasal neurons by odorous cues from conspecifics can lead to changes in innate behaviors in association to e.g. mating and aggression. Given the role of the organ in detecting odorous molecules important for species-specific communication, investigations of the structure of the vomeronasal organ within the mammalian group are warranted. Wild Scandinavian moose (Alces alces) is an even-toed ungulate (order: Artiodactyla) and the largest representative of the deer family Cervidae. This is the first study of the vomeronasal organ of a deer species that includes immunohistochemistry. The gross anatomy of the tubular vomeronasal. organ of moose was investigated including a nasopalatine duct that may allow for entrance of odorous substances from the oral and nasal cavities. The histology of the neuroepithelial part, in moose of both sexes, appeared overall similar to that of representatives of other Artiodactyla families. Basement membrane, structural epithelial cells, glia and sensory neurons were analyzed by expression of specific markers. The results suggest that the vomeronasal neuroepithelium of even-toed ungulates is more similar in organization to that of carnivores than e.g. rodents with regard to the relative number of sensory neurons and presence of functionally distinct populations of neurons. (C) 2009 Elsevier B.V. All rights reserved.