The ultrastructure of rabbit tracheal epithelium was studied 20 min after injection of 0.04 and 0.5 mg of atropin. The tracheae were lined with altered ciliated pseudostratified columnar epithelium. The degree of damage to the epithelial cells was dose dependent. The injury to the tracheal epithelium due to treatment with 0.04 mg of atropin was considered mild. The administration of the higher dose of atropin caused moderately severe epithelial damage. Both experimental groups exhibited morphological signs of impaired self-cleaning ability.