Dialyzers today are developed with high permeability and biocompatibility in mind, even though the definition of these so-called high-flux dialyzers remains controversial. In the Japanese reimbursement system, dialyzers are divided into five types, ranging from I to V, in accordance with their clearance for beta2-microglobulin (beta2-MG). Classes IV and V (beta2-MG clearance greater or equal to 50 and 70 ml/min, respectively, at a blood flow rate of 200 ml/min) are the most common ones, used in more than 90% of Japanese dialysis patients. Membranes used in types IV and V dialyzers are called high-performance membranes (HPMs) and are characterized by an exceptionally high flux rate, permeability and biocompatibility. The book at hand covers all aspects of these HPM dialyzers, including their definitions and characteristics, clinical experiences and basic investigations. Moreover, historical HPMs and several membranes with special characteristics that are not categorized into classes IV or V are discussed. Providing a summary of commercially available HPM dialyzers, this publication not only serves as a textbook for those interested in state-of the-art dialysis treatment, but is also a concise database of the products available.