Airway sampling is a very important component of the diagnostic work up of respiratory cases, and in many instances it is the method that will give a definitive diagnosis since the results of such tests will reflect lung and airway pathology. Until routine lung biopsy is adopted in companion animal medicine, airway sampling will remain one of the most important diagnostic tests in respiratory medicine. The main use of airway sampling is to obtain samples for cytological analysis. In addition, airway sampling can allow identification of significant bacterial infections and can identify respiratory parasites. However, culture might not always be successful and the veterinary surgeon has to be wary of false-negative results or erroneous positive results (i.e. culturing organisms that are of no concern). The chapter looks at Tracheal wash and bronchoalveolar lavage; Bronchoscopy; and Cytology and culture.