Kidney transplants from living donors have a higher survival rate than cadaveric kidneys probably due to shorter ischemia time. We hypothesized that intraoperative kidney oxygenation (kox) predicts postoperative transplant function. Thus, we measured kox (microvascular hemoglobin oxygen saturation in %) by reflectance spectrophotometry and microcirculatory kidney perfusion by laser Doppler flowmetry (O2C, Lea, Germany) 5 and 30 min after kidney reperfusion on the surface of the transplant in 53 renal transplant patients. Kox improved 30 min after reperfusion compared to 5 min (from 67 to 71%, p<0.05) probably due to higher oxygen extraction shortly after reperfusion. Kox correlated with mean arterial blood pressure and central venous pH (p<0.01). Most importantly, kox was significantly higher in kidneys from living compared to cadaver donors (74 vs. 63%) and in kidneys with good as opposed to those with poor postoperative function (71 vs. 45%). Finally, kox correlated positively with cold ischemia time and postoperative creatinine clearance and negatively with plasma creatinine, need for hemodialysis and hospital length of stay. Thus, the intraoperative measurement of tissue oxygenation in kidney transplants is predictive of early postoperative kidney function. Further studies should look at the effects of therapeutic maneuvers aimed at improving kidney oxygenation intraoperatively.