DESCRIPTION (provided by applicant): Autosomal dominant polycystic kidney disease (ADPKD) is a major cause of disabling morbidity and is the fourth leading cause of end-stage renal failure in the world, affecting more than 500,000 U.S. citizens and millions more worldwide. Researchers at the University of Alabama, Emory University, University of Kansas, Mayo Clinic and Washington University St. Louis joined together in 2000 to create the Consortium for Radiologic Studies of Polycystic Kidney Disease (CRISP-I). The primary objectives of this investigation were to: (1) Develop and test the accuracy and reproducibility of imaging techniques to monitor changes in renal cyst size and parenchymal involvement. (2) Establish and maintain a database of uniformly and accurately collected information. (3) Maintain and make available such data to facilitate the planning and implementation of clinically appropriate interventions in the near future. The goals of CRISP-I I are to extend the observations of CRISPI in order to: 1) Draw unequivocal linkage between the rate of kidney/cyst enlargement and qualitative and quantitative end-points. 2) Provide a marker of disease progression (kidney volume) sensitive and accurate enough to be used as a primary outcome marker in clinical trials aiming to forestall disease progression. 3) Develop and test other bio-markers of disease progression. The specific aims are: Aim 1: Extend the preliminary observations of CRISP-I to ascertain the extent to which quantitative (kidney volume and hepatic and kidney cyst volume) or qualitative (cyst distribution and character) structural parameters predict renal insufficiency. Aim 2: Extend the preliminary observations of CRISP-I to ascertain the extent to which age and sex-adjusted measurements of renal blood flow by MR technology predict the rate of renal growth; and, renal blood flow and kidney volume predict the rate of renal function decline in ADPKD. Aim 3: Exhaustively analyze the living database and stored biologic samples derived from CRISP-I and the CRISP-II extension to develop and test new metrics to quantify and monitor disease progression, and collect DMA samples and clinical information from CRISP family members known to have ADPKD for use in future studies to examine genotype-phenotype correlations and to identify genetic modifiers.