In recent years the concept of biocompatibility is not limited to the dialytic membranes, but has been substituted by a more general viewpoint where all the parameters of the dialytic treatment are taken into consideration: the interaction of blood-surfaces (the dialyzer in all its components and the hematic lines), the sterilization of all materials, the quality of the solutions utilized for dialysis and reinfusion. Numerous studies have shown that the inflammatory response in dialysis is the cause of many of the side effects of dialytic treatment itself both acute and chronic. Hypoxemia, 'first use' syndrome, hypotension, allergic-anaphylactic reactions (short-term side effects); microinflammation, malnutrition, accelerated arteriosclerosis, anemia, beta2 microglobulin amyloidosis, immunodeficiency, bone mass loss (long-term side effects), have all been reported. In this review, we will focus on the fluids utilized for hemodialysis (HD) and hemodiafiltration (HDF); we will describe the process of disinfection of the machines which produce the dialytic solutions.