Beginning in 1966, the Patient Registration Committee of the Japanese Society for Dialysis Therapy has conducted a survey once a year on renal replacement therapy in Japan. As of 1983, the survey covered the life/death of patients in the survey years, as well as the case mix of individual patients. In 1990 several laboratory variables were added to the survey items. The present report summarizes the data from the 1993 and 1994 surveys. The Committee mailed out questionnaire forms at the end of the survey year to the heads of all dialysis facilities. Survey forms were returned from 99.6% of the dialysis facilities in the 1993 survey, and from 99.8% of the facilities in the 1994 survey. Some 143709 patients were treated by renal replacement therapy in 1994 (7509 were treated by CAPD, and 131016 by extracorporeal haemopurification). The gross mortality rate was 9.5% in the same year. The mean values of the laboratory variables among 88693 patients undergoing thrice weekly haemodialysis were as follows in 1993: Kt/V, 1.31 +/- 0.30; protein catabolic rate, 1.04 +/- 0.30 g/kg/day; haemodialysis time, 4.12 +/- 0.50 h. In 1994, the variables were: predialysis serum creatinine concentration, 11.54 +/- 2.85 mg/dl; predialysis serum albumin concentration, 3.91 +/- 0.55 g/dl; predialysis haematocrit, 28.69 +/- 4.36%.