The morphologic changes of olfactory epithelium in the absence and the presence following absence of air flow for various time periods were observed to clarify the role of the air flow in maintaining the normal function of the tissue. Although the importance of the air flow in maintaining normal morphology of the olfactory epithelium had been reported by Früward (1935) and Lee(1988), these results are not conclusive by demonstrating different degree in the extent of the changes by study methods. Thirty-four Korean rabbits, weighing 1-1.5kg, were used. The animals were grouped into 2, one for the blocking and the other for the blocking and unclosing of air flow. For the blocking of air flow, one of the anterior nares was sutured to block the air and left for 1, 2, 4, 8 and 12 weeks. For animals in the other group, the anterior nares obstructed for the experimental periods was opened by removing the sutures, and left for an additional 6 weeks. The animal were then anesthetized and perfused intracardially with 2.5% glutaraldehyde fixative. The olfactory epithelium was obtained from the septal area. Changes in surface and intracellular structures were examined by use of a scanning and a transmission electron microscope. Degenerative changes of the olfactory epithelium at the olfactory cell layer were obvious at the first week in the absence of the air flow. The surface areas appeared to be mainly composed of supporting cells, which suggested that almost all of the olfactory mat and vesicles had been disappeared, if any, they were cells with shrunken vesicles, leaving the supporting cells only. At two weeks in the absence of the air flow, gradual regeneration of olfactory cells was suggested by noting the reappearance of olfactory cilia. However, the most part of the surface was remained as area composed of supporting cells without noticeable olfactory vesicles. Thereafter the number of olfactory cells and the olfactory cilia as well as the length of the cilia were found to be increased to some extent though it was still subnormal. The observed olfactory vesicles were not matured type. When the air flow was reestablished, normal olfactory epithelium was noted among the shrunken olfactory vesicles, regardless of the period of obstruction. These all together suggested that the absence of the air flow affected the layer of the olfactory cells to be decreased. Although regeneration of the olfactory cell was observed, the maturation of olfactory vesicles was not complete. The restoration of the air flow induced some of olfactory vesicles appeared to be complete. Thus the presence of the air current, if the morphologic characteristics represent the functional characteristics, might be one of important factors in maintaing the olfactory cells in normal status.