Polycystic kidney disease (PKD) is a well-documented abnormality in domestic cats, particularly in breeds of Persian origin. Investigators at the Laboratory of Genomic Diversity (LGD) of the National Cancer Institute will collaborate with the researchers at Kansas and Ohio State Universities to identify one or more candidate genes for feline polycystic kidney disease. Three generations of affected cats will be recruited to participate. Blood samples will be collected from these cats to develop a genetic test to identify PKD cats at a very early age. The goal of the study is to make earlier detection possible with a simple blood sample or cheek swab so that affected individuals can be eliminated from planned breedings.