A diagnosis of a specific viral disease in the cat involves a combination of an accurate history, careful observation of disease signs, demonstration of characteristic clinical pathologic changes, and isolation or identification of the virus. Isolation or identification of a virus from the patient does not establish that the disease observed was caused by the virus so isolated or identified; correlation and proper interpretation of all findings are necessary to establish a diagnosis. Virus identification may involve office laboratory tests, such as cytology or ELISA, or more specialized procedures. Whether specimens are to be sent out for specialized tests or office laboratory procedures are to be used, the veterinary practitioner must not only know what specimens are required but must also understand the test and be able to properly interpret the results in light of the patient's observed condition.