There is a critical need for safe and effective analgesics treating pain associated with the most common disease of cats – degenerative joint disease (DJD). This is particularly important in such populations of cats with chronic kidney disease (CKD) where current analgesics (pain-killers) are considered to be associated with a risk of toxicity. The biggest impediment to development of analgesics in cats has been the difficulty in measuring pain. Several sources of evidence suggest that DJD-pain in cats is due to an altered state of immune function, resulting in inflammatory mediators (such as substances called cytokines and chemokines) building up in the body and producing pain. Researchers here believe cytokine/chemokine profiles in the blood can be used as a measure of DJD-associated pain, and further, that cytokine/chemokine profiles will lead them to novel targets for the development of effective, safe analgesics in cats, especially in cats with concurrent DJD and chronic kidney disease (CKD). In this study, the proposal is to measure these inflammatory mediators in groups of cats from which they have extremely detailed clinical information and have already collected the samples. The pilot data indicates they will successfully identify differences, and the results of this study may lead to a biomarker (or biomarker profile) measurement of chronic pain associated with DJD or DJD and CKD – essentially, a ‘blood test’ for chronic pain. Additionally, evaluation of the differences between groups may lead to discovery of the mechanisms of pain in these cats, or even the mechanisms of these chronic diseases.