A 7-year-old mixed-breed cat presented with intermittent dry cough for 2 years. Histological examination of the lung biopsy revealed hyperplasia of bronchial and bronchiolar epithelium, and intraepithelial infiltration of globule leukocytes in many bronchi, bronchioles, and terminal bronchioles. Lymphoid aggregates cuffed airways, respiratory bronchioles, and alveolar ducts. Terminal airway inflammation was associated with type II pneumocyte hyperplasia within adjacent alveoli. Warthin-Starry stain revealed numerous argyrophilic and filamentous bacilli that were interspersed or clustered with cilia of the respiratory epithelium. The morphology, distribution, and gram (negative) and ultrastructural characteristics were consistent with cilia-associated respiratory (CAR) bacillus. Real-time polymerase chain reaction assays using paraffin-embedded lung tissue confirmed the presence of