Several noninfectious nonneoplastic interstitial lung diseases (ILDs) have been recognized in dogs and cats. Overall, these ILDs are poorly characterized in dogs and cats, although awareness of the conditions based on descriptions of clinical case series may be increasing. Lung biopsy remains crucial to the diagnosis, characterization, and classification of ILDs. Histopathologic findings can help to guide clinicians in selecting appropriate therapy and providing an accurate prognosis to pet owners. Only with definitive recognition of these pulmonary conditions can our knowledge of the clinical course and response to therapy be improved.