[Biocompatibility in long-term hemodialysis: facts--theories--clinical significance]

Biocompatible hemodialysis membranes do not cause major untoward effects due to blood-interface reactions. In principle, however, every component of the extracorporeal circuit may have detrimental effects. Biocompatibility parameters include for example complement components, leukocyte drop, elastase release and interleukin-1 generation. Furthermore, ethylene oxide sensitization, beta 2-microglobulin clearance and endotoxin contamination are of importance. The clinical relevance of biocompatibility in modern hemodialysis is critically discussed.