Hemodiafiltration (HDF) for the treatment of end-stage renal disease patients is predominantly performed in European countries and in Japan, with some differences in technique such as rate of blood flow and dialysis fluid delivery systems. The main focus of this book is on the clinical importance of online HDF, the techniques of which have been re-evaluated with the introduction of super high-flux membrane dialyzers. After a brief introduction into the history of HDF, recent advances and clinical experiences of HDF are summarized, including water quality control for dialysis fluid, equipped system for safe use, clinical advantages, and theoretical aspects of HDF. Moreover, at the end of each chapter researchers and scientists discuss problems into which further research is needed. Clinicians and scientists involved in the treatment of end-stage renal disease patients will find this publication an essential source of information. Moreover, it may also serve as a textbook for those who are planning to start HDF in their clinics or who are studying blood purification therapies in medical schools, nursing schools and even in engineering schools related to medical technologies.