Histological observations were made on the nasal cavities of 3 tree shrews, 2 slow lorises, 2 macaques and 1 gibbon. A naked rhinarium was seen in the two prosimian primates, whereas the snouts of the simian primates were lined by hairy skin. Other differences were the presence of vomeronasal organs and a wider distribution of olfactory mucosa in the nasal fossae of the prosimian primates. The respiratory epithelium of the prosimian primates consisted of a pseudostratified columnar ciliated epithelium. In the simian primates, this epithelium showed a tendency to become stratified. Only serous glands were seen in the respiratory mucosa of the prosimian primates while both serous and mucous glands were present in the simian primates.