A disorder caused by congenital ciliary dysfunction occurs in dogs. Most of the clinical signs are directly or indirectly attributable to immotile or dyskinetic cilia and spermflagella. Due to severely impaired mucociliary clearance, a continuous mucoid nasal discharge and intermittent sneezing and coughing are typically observed during the neonatal period. Recurrent bacterial rhinosinusitis and bronchopneumonia usually start within a few weeks of birth. Hypoplastic nasal sinuses and atresia of the frontal sinuses are variable features of the disease that may be caused by neonatal colonization of these structures by specific bacteria. Bronchiectasis is an acquired lesion resulting from chronic inflammation and obstruction of airways. A secretory otitis media is caused by dysfunction of the cilia in the middle ear, and is manifested in some dogs by sclerotic tympanic bullae. Male infertility is caused by live, but immotile to hypomotile spermatozoa; however, unexplained oligospermia and azoospermia have been reported. Hydrocephalus and situs inversus are common but variable features of the disease; the genesis of these lesions has not yet been determined. The probable mode of inheritance is autosomal recessive, but dominant mutations cannot be excluded. The diagnosis can be confirmed by demonstrating the absence or near absence of nasal or tracheal mucociliary clearance and the presence of a specific ultrastructural lesion in a large percentage of cilia from multiple sites (airways, middle ear, or oviduct). The ultrastructure of sperm flagella should mirror that of the cilia. Not all dogs have ultrastructural ciliary lesions, and in these cases, results of in vitro analysis of ciliary activity may be highly suggestive, if not diagnostic. In dogs without mucociliary clearance in which structural and functional analysis of cilia are not diagnostic, confirmation of congenital ciliary dysfunction can be established only by ruling out other diseases with similar signs (e.g., congenital immunodeficiency syndromes). The clinical course in an longevity of affected dogs are highly variable. Appropriate antibiotic treatment and pulmonary physical therapy may result in prolonged survival, although cor pulmonale and reactive systemic amyloidosis are potential sequelae of chronic hypoxia and chronic bacterial infection of the airways, respectively.