Hyposmia following laryngectomy is a well-known clinical observation, yet the causes have been controversial for many years. In an attempt to resolve this issue, an animal model was constructed. Eighteen dogs were divided into three equal groups: control dogs, dogs that underwent tracheostomy, and dogs that underwent tracheostomy and denervation of the larynx, simulating total laryngectomy. Four to 6 months following these operations, biopsies from olfactory mucosa were taken. The results showed marked changes in the olfactory mucosa of the two test groups: cystic degeneration of secretory glands in the olfactory mucosa of the first group and involution of the olfactory mucosa, substituted by dense connective tissue and "ballooning" of olfactory nerve fibres in the second group. These findings suggest that the changes in olfactory mucosa are not only caused by a loss of nasal airway but also the existence of a neurologic connecting network between the vagus nerve and the olfactory cortex.