This study was designed to evaluate the potential applications of magnetic resonance imaging for the diagnosis of early and sequential changes of acute renal ischemia. Renal isehmia was induced in seventeen rabbits by surgical ligation of the left renal artery. Magnetic resonance imagin(MRI) was performed with a 2.0T superconductive MR system and a spin-echo technique was used with echo times(TE) of 30 and 80 msec and repetition times(TR) of 0.5 and 2.5 seconds. Kidneys were evaluated before and up to 48 hours after left renal artery ligation, and the spin echo images were analyzed for intensity difference and T1, T2 relaxation times between the cortex and the medulla of both kidneys. After one, and one and half hour following ligation of the left renal artery, the kidneys showed a 4-20% decrease in the left cortex compared to the right cortex contrast uptake(CCC) (P<.01). There was a 14-29% decrease in left medulla to right medulla contrast uptake(MMC) (P<01). A 29-147% incre se in contrast uptake was noted when the left cortex was compared to the left medulla (P<.05). There was a 51-68% decrease in CMC of the right kidney (P<.05) on three different spin echo images. In the cortex of the left kidney, T2 relaxation time decreased 14% (P<.01). CCC and MMC showed more prominent changes than CMC, and sequential changes of CCC and MMC were most prominent on T2 weighted images with TR = 2.5sec and TE = 80msec when compared with compared with T1 weighted and proton density weighted images. Twelve hours after renal arterial ligation, T2 relaxation time, CMC, CCC, and MMC returned to normal values and these findings were believed to be due to congestion and collateral blood supply. In renal ischemia, the most useful MRI findings for diagnosis were found to be changes of CCC and MMC on T2 weighted image, and T2 relaxation time of the cortex in the ischemic kidney.