PURPOSE: To evaluate the usefulness of MR imaging in the differential diagnosis of the underlying causes of early-stage acute renal failure (ARF) by comparing the MRI findings of experimentally-induced crescentic glomerulonephritis (CGN) and acute tubular necrosis (ATN) in rabbits. MATERIALS AND METHODS: Experimental CGN was induced by injecting anti-glomerular basement membrane antibody into six rabbits, and ATN by injecting glycerol solution into six rabbits. A normal control group of three rabbits was also used. Renal MR imaging (T1-and T2-weighted coronal images and dynamic MRI : DMRI) was performed the day before, and one, four, and seven days after the induction of CGN; and immediately before, and four, and eight hours, and one, four, and seven days after the induction of ATN. Sequential renal gun-biopsies and blood sampling (serum creatinine, sCr) were performed. Renal area, corticomedullary differentiation(CMD), and the passage of Gd-DTPA (pattern of dark band), as seen on MRI, were analyzed and correlated with serial change of sCr. RESULTS: In normal kidneys, CMD was clearly apparent on both T1- and T2-weighted images. DMRI demonstrated a progressively inwardly migrating dark band in the kidneys. CMD was relatively clearly demonstrated in the ATN group but less clearly identified in the CGN group. Renal size (area) and sCr gradually increased in both the CGN and ATN groups, and dark bands were moderately to poorly defined in both. CONCLUSION: We conclude that DMRI could be used to differentiate and evaluate disease processing and compromised renal function in cases of CGN and ATN. On T1- and T2-weighted images, CMD was relatively well preserved in the ATN group, but was less clear in the CGN group. These MRI findings may be helpful for differentiation of the underlying causes of early-stage ARF, particularly between CGN and ATN.