Respiratory disorders are among the most common problems leading horse owners to seek veterinary attention. Accurate diagnosis of these conditions allows for proper treatment to be instituted, much to the benefit of the patient and satisfaction of the client. As an introduction to this issue on equine respiratory disorders, we review some of the tools that are available to equine veterinarians for the diagnosis of respiratory disorders. Physical and endoscopic examination, radiology, diagnostic ultrasound, techniques for sampling the respiratory tract, hematology, blood gas analysis, respiratory mechanics, and some modern diagnostic tools are briefly covered.