Changes in the nuclear magnetic resonance (NMR) parameters of spin-lattice relaxation (T1), spin-spin relaxation (T2), proton density (rho), and water diffusion (DNMR) were measured over time together with the histopathological status in three regions of rat brain cortex after permanent middle cerebral artery occlusion (MCA-O). Histological response ranged from severe irreversible damage (necrosis and cavitation) to relatively mild and apparently reversible damage. DNMR was the only NMR parameter which demonstrated a statistically significant change in all three regions of brain studied. Additionally, rho was significantly increased only in the region of brain studied which eventually progressed to necrosis and cavitation. Finally, data are presented which indicate that changes in T2, DNMR, and rho can occur independently of one another.