The concentration of bacteria and endotoxin in dialysis water and dialysate of 30 dialysis centers in western Germany was examined. Water samples were obtained after treatment by reverse osmosis or other processing methods. Collection of dialysis samples for bacterial, fungal, and endotoxin analysis was conducted before and 2 hours after start of hemodialysis. In 17.8% of all water samples analyzed, the AAMI standard was exceeded and bacterial and fungal counts greater than 200 colony forming units/ml were found. In 11.7% of all dialysate samples, higher contamination than the recommendations for dialysate of 2000 colony forming units/ml were found. The concentration of endotoxin in water and dialysate varied between 0 and 95 endotoxin units in the water samples and 0 and 487 endotoxin units/ml in the dialysate samples. In 12.2% of all water sampled, and 27.5% of all dialysate samples, values of 5 endotoxin units/ml were found. No correlation was found between the level of contamination of either water or dialysate in a specific center and the following factors: water processing method (reverse osmosis or others), type of dialysate (acetate of bicarbonate), type of dialysate machine, or method of machine disinfection. In view of these results it is suggested that endotoxin testing, especially in the dialysate, be a part of regular quality control in dialysis.ASAIO Journal1994; 40:1012-1016.