The most likely cause of graft pancreatitis is the ischemia/reperfusion injury which can be a major problem in simultaneous pancreas-kidney transplantation. Animal experiments suggest the important role in this process of an impaired microcirculation after reperfusion. We have investigated pancreatic microcirculation in the early reperfusion period during clinical pancreas-kidney transplantation. Tissue PO2 (PO2ti) was monitored by a PO2-sensitive electrode. After reperfusion (a.r.) samples were taken from the venous effluent of the pancreas and simultaneously from the radial artery. After an initial peak a transient fall of PO2 was found. Total blood flow and hemoglobin oxygen saturation (sHbO2) in the venous effluent increased until 90 min a.r. (107 ml/min, 97.1%) High venous sHbO2 and high PO2ti correlated with good graft outcome. These findings can be explained by an impairment of capillary perfusion (no reflow) and concomitant shunt perfusion. The data suggest the considerable relevance of pancreatic microcirculation in the early reperfusion period during clinical pancreas transplantation.