This study was designed to evaluate the potential applicability of magnetic resonance imaging (MRI) for the diagnosis of acute renal vein thrombosis. Renal veing thrombosis was experimentally induecd by surgical ligation of the left renal vein in a total of 21 rabbits. MRI was performed with a 0.5 Tesla superconductive magnetic system. Spin echo technique was used with varying TR and TE parameters. Spin echo images of the rabbit kidney were analysed for morphology and signal intensity. T1 and T2 relaxation times of the renal cortex and medulla were calculated from the images. After venous ligation, kidneys became enlarged. Low signal band along the outer medulla in T2 weighted images were characteristically shown from 1 hour to 3 days after ligation. Changes of cortex to medulla contrast (CMC) values were significant (p<0.05) in T1-and T2- weighted images of the ligated side. T1 and T2 relaxation times were significantly prolonged (p<0.05) on the ligated side, both in the cortex and medulla from 1 hour to 2 weeks after the ligation, while T2 relaxation time on the contralateral side was significantly prolonged both in the cortex and medulla 2 weeks after venous ligation. The most useful MRI criteria for the diagnosis of renal vein thrombosis were enlarged renal size, and the low signal band along the outer medulla of ligated kidney. The relative intensity difference between cortex and medulla (CMC) in T1-and T2 -weighted images, and T1 and T2 relaxation times were suggested to be the useful MR parameters for the diagnosis of acute renal vein thrombosis.