Although chronic kidney disease (CKD) is one of the most common diseases that affects elderly cats, few tests are currently recommended for diagnosing early-stage CKD and forecasting disease progression. In humans and dogs, homocysteine (Hcy) has been associated with certain aspects of renal dysfunction, including a positive correlation to systolic blood pressure in humans. Because it can be difficult to obtain blood pressure readings and to predict and track early renal disease in hospitalized cats, the authors investigated the potential applications of Hcy in feline CKD diagnostics. In this study, Hcy increases could be correlated to International Renal Interest Society (IRIS) stage; however, significant differences between IRIS groups were not always present. A significant difference was not found between concentration of Hcy and degree of proteinuria, and no correlation was found between high Hcy levels and hypertension. Thus, the authors concluded that serum creatinine provides more reliable information than Hcy concentration for purposes of early identification and staging of CKD in cats.