To assess the effects of renal ischemia and reperfusion on in vitro magnetic relaxation times (T1 = magnetization recovery, T2 = spin echo), the spectroscopic characteristics of the renal cortex from 25 rabbits were evaluated. Eight served as controls (group 1), 9 had 1 renal pedicle ligated for 1 h (group 2) and 8 (group 3) were occluded for 1 h and reperfused for 30 min. For intraanimal comparison purposes, % H2O content, T1 (ms), and T2 (ms) of the ischemic (reperfused) kidney were normalized to the values from the normal kidney within the same animal. Renal ischemia consistently increased water content, which was exaggerated by reperfusion. In association with ischemia, T1 fell and with reperfusion T1 lengthened. T2 increased with ischemia and declined from the peak ischemic effects with reperfusion.