The Final Report of the USA CAPO Registry summarizes eight years of observation and analysis that reflects the experiences of 485 clinical centers and over 25,000 CAPO patients. As such, it offers a wealth of information, available here for the first time to interested parties around the world. Because the National Institutes of Health was quick to see the potential of CAPO as a promising therapy for patients with end stage renal disease, the Registry project was begun soon after its introduction into clinical practice in the USA. Accordingly, the Registry offered the nephrology community in the United States a special opportunity to study this emerging new therapy in some detail, an opportunity not previously available for any other form of dialysis. As will be seen in this report, the result of this early and intensive research effort has been the development of a vast amount of clinically important information regarding the utilization, safety, and efficacy of this important dialytic therapy.