Peritoneal dialysis was performed in 18 uremic patients using both room temperature (27-31 degrees C) and prewarmed (37 degrees C) dialysate. There were no significant differences between the two periods of the following parameters: urea clearance, creatinine clearance, inulin clearance, ratio of inulin to urea clearance, ratio of inulin to creatinine clearance, drainage volume, dialysate flow rate, ultrafiltration rate and total protein loss. Since the peritoneal dialysis efficiency was not improved by warming dialysate in this range of temperature, the warming procedure is not necessary in the countries where the average room temperature is 29 degrees C (27-31 degrees C). The exclusion of this procedure will decrease the work load and lessen the chance of dialysate contamination.