Cattle appear to be more susceptible to respiratory disease based on anatomic and physiologic factors. Diagnostic sampling and tests can provide valuable information when investigating causes of respiratory disease within a group of cattle. Diagnostic tests should be selected based on several criteria including quality of the sample, diagnostic question, producer goals, history, diagnostic laboratory, diagnostician, and economy. Veterinarians and producers should agree on the diagnostic question, testing goals, and use of results before submitting samples.