Much prognostic pessimism has been associated with polycystic disease of the kidney. When the variability of the clinical manifestations and course of this not uncommon clinical entity is considered, the pessimistic prognosis is oftentimes unwarranted and unjust to the patient. The present study was undertaken to elaborate further on the various aspects and manifestations of the disease that, when properly evaluated, permit the physician to outline treatment more accurately and prognosticate in a given case. PATHOGENESIS The pathogenesis of polycystic disease is not completely understood. The various theories of etiology that have been proposed were summarized by Rall and Odel1under the categories of metabolic, inflammatory, neoplastic, and developmental defects. Since Rall and Odel covered this aspect of the condition, we will mention only two recent contributions. Experimentally, Bagg2has been the only one successful in producing a true polycystic kidney. He treated the abdomens of mice with