BACKGROUND: The changes in acid-base balance and serum electrolytes after infusion of 0.9% normal saline during renal transplantation are poorly characterized. In this study, the relationships between the infusion of fluids and the changes in arterial blood gas analysis, serum electrolytes and central venous pressure during renal transplantation were determined. METHODS: Sixty-seven patients undergoing elective renal transplantation were divided into two groups: group I (n = 33) was made up of patients who received a living related renal transplantation, while group II (n = 34) was made up of those who received a living unrelated renal transplantation. Blood gas analysis, central venous pressure and serum electrolytes were evaluated just after the beginning of the operation, just before reperfusion (unclamping of the renal artery and vein), just after reperfusion and 20 minutes after arriving in the recovery room. RESULTS: pH, base excess, HCO3 and Na+ concentration were decreased, but PaCO2 was not changed during the operation. Central venous pressure and K+ concentrations were elevated during the operation. CONCLUSIONS: The results of this study suggest that 0.9% normal saline and mannitol leads to dilutional acidosis. If a lot of fluids are required during transplantation, we need to consider that 0.9% normal saline can aggravate acidosis in a renal transplantation patient.