Na-K-ATPase activity and "in vitro" PAH uptake were used to determine the possible presence of ischemic injuries in cadaver kidneys after different periods of cold storage, and the data were compared with those obtained for an experimental rabbit group. In rabbit kidneys, Na-K-ATPase activity remained stable up to 168 h of cold storage in the outer medulla and superficial cortex, and PAH uptake decreased significantly after 72 h. In human kidneys, Na-K-ATPase activity in the outer medulla was low during the first phase of the study (cold storage less than 20 h), suggesting early injury to the thick ascending limb of Henle's loop. In the superficial cortex, no apparent progression of injury was observed between PAH uptake and Na-K-ATPase activity. In conclusion, our results suggest the presence of early signs of injury in the thick ascending limb of Henle's loop and preservation of proximal tubule function in cadaver kidneys for up to 70 h of cold storage.