Kidney cortical and medullary“spin-lattice”(T1) and“spin-spin”(T2) relaxation times were measured by spectroscopy in several types of experimental renal failure in rats. The T1, and the measured tissue water content were used to calculate the fraction bound (FB) and hydration fraction (HF) according to a fast proton diffusion model. The present study demonstrated the possibility to differentiate between normal and pathological renal tissue resulting from renal artery clamping (RAC), renal pedicle clamping (RPC) with or without reflow, glycerol-induced acute renal failure with or without previous dehydration, and chronic hypertensive renal failure induced by 5/6 nephrectomy and saline loading, with low (6%) or normal (21 %) protein diet. Shortened T1, and prolonged T2found in both cortex and medulla of the glycerol-induced ARF in dehydrated rats seem to represent a MR ischemic pattern. The prolongation of T1and T2and the increase in water content in the other groups seem to relate to different amounts of tubular obstruction and renal congestion. In summary, characteristic MR properties of different types of renal failure may provide etiological and pathogenetic diagnostic possibilities.