Progressive apoptotic loss of non-cystic nephons has recently been shown to be an important pathological feature associated with the development of polycystic kidney diseases (Woo, NEJM 333:18-25, 1995). In contrast to the high vascularized, blood red appearance of normal kidneys, end-stage polycystic kidneys from human patients and from animal models are pale and translucent and seldom bleed when punctured. I therefore reasoned that the renal vasculature must also be greatly abnormal and perhaps absent in end-stage polycystic kidneys. I propose to use ex-vivo magnetic resonance microscopy to characterize the renal vasculature of polycystic kidneys from two mutant mouse strains and one mutant rat strain that develop congenital polycystic kidney diseases. I estimate that imaging 4-5 normal and 4-5 polycystic kidneys at different stages of disease progression harvested from each of the three rodent models of polycystic kidney disease should provide a comprehensive picture of the fate of the renal vasculature in the development of polycystic kidney diseases in these models.