It has generally been accepted that biological contamination of dialysate deteriorates the biocompatibility of dialysis therapy and accelerates dialysis-related complications such as dialysis-related amyloidosis (DRA) and malnutrition-inflammation-atherosclerosis (MIA) syndrome. During the past decade several studies have clarified that very slight amounts of contamination can lead to inflammatory response, and we could not confirm biological dialysate quality only by measuring endotoxin levels despite of measuring viable cell counts or biofilms. To achieve this, the European Renal Association/European Dialysis Transplantation Association and the American National Standardization Institute/Association for the Advancement of Medical Instrumentation published new standards for dialysate, in which very strict control levels were recommended with regard to viable bacterial cell counts. In 2004 JSDT raised the required standard of the levels of endotoxin, and began to develop a standard for bacterial cell counts. In Japan, many chronic kidney disease patients are treated with centralized dialysate supply systems which have weak spots in disinfecting the system. This causes some difficulties in making a standard for viable bacterial cell counts. In the present paper, we summarize evidences of clinical usefulness of ultrapure dialysate and perspectives of the standard for dialysate in Japan.