Massive air embolisation (persufflation) of four machine-perfused human kidneys occurred during preservation. This lasted for 60–120 min and caused increasing perfusion resistance. Pressure and flow returned to normal within 2 h after reperfusion. All kidneys showed immediate function after transplantation. Experiments with dog kidneys revealed closure of cortical vessels and increased kidney temperature during persufflation. Cortical flow became normal after 1 h of reperfusion.