Regular bacteriological control examinations of the dialysate may contribue to the elimination of pyrogenic and even septic reactions. Regular checks of HBS-Ag and HBS-Ab are an effective measure in the early diagnosis of hepatitis B, which is characteristically anicteric and follows a prolonged course in patients on regular dialysis treatment (RDT). Virological examinations can be helpful in the diagnosis of cytomegalovirus (CMV) disease in certain cases of unexplained fever. Regular bacteriological examination of the urine is important in the detection of a urinary tract infection possibly necessitating binephrectomy prior to transplantation. After renal transplantation bacteriological control examinations of the urine, determinations of HBS-Ag and HBS-Ab, complement-binding reactions to CMV and mycotic cultures from the throat, sputum and urine should be regularly performed. Urinary tract infections may be found in up to 88% of the transplanted patients. Hepatits-B infection was noted in 62.8% of this case material. Positive Candida albicans cultures from samples of the uurine usually indicate systemic Candida albicans infection. The described diagnostic measures contribute to an effective prophylaxis and therapy of infective complications in patients on RDT and after renal transplantation.