Magnetic resonance imaging (MRI) has been used widely in the diagnosis of acute spinal cord injuries. The association between MRI findings and histologic changes, however, remains unclear. Using a rabbit spinal cord injury model, the authors compared the MRI and histologic abnormalities as they evolved over the first post-trauma month. Bleeding in the gray matter, visualized as a low-intensity area on T1-weighted views and high-intensity area on T2-weighted views, observed immediately after injury, disappeared within the first week. Edema, appearing 6 hours after the initial injury and seen as a high-intensity T2-weighted MRI image, became maximal 1 week later and gradually decreased thereafter. Also appearing 1 week later, were necrotic changes in the gray matter, corresponding to low signals on T1-weighted studies but high signals on T2-weighted studies. MRI therefore helped differentiate hemorrhage and necrosis, presumably irreversible lesions, from the more reversible findings related to edema.