The microstructure of olfactory and vomeronasal organs in four amphibians and reptiles were examined by light microscopy.The results showed that vomeronasal organ began to differentiate from nasal sac and was located in the lateral side of the olfactory organ in Batrachuperus tibetanus,but it was still underdeveloped.Although olfactory and vomeronasal organs were co-localized in the nasal sac in Feirana quadranus,vomeronasal organ was more developed.There were developed vomeronasal gland around vomeronasal organ and vomeronasal organ was connected with olfactory organ through a fine pipeline.Vomeronasal organ and nasal cavity were separated completely and formed two independent sacs in Gloydius qinlingensis and Trimeresurus jerdonii,and nasal cavity further differentiated into olfactory epithelium and respiration epithelium.These results suggest that the vomeronasal organ first appears in Caudata,further differentiates in Anura,and becomes an independent organ in snake.The vertebrate adaption of land living directly results in the formation of vomeronasal organ which is the feature of tetrapod.