Subacute necrotizing encephalomyelopathy (SNE) is a genetic disorder of pyruvate metabolism. Until recently the diagnosis of SNE could only be made at autopsy. However, an antemortem diagnosis can now be suggested by the correlation of clinical and laboratory data with computed tomography (CT) and/or magnetic resonance imaging (MRI). Five children with clinical and laboratory data suggesting the diagnosis of Leigh disease were evaluated by CT and MR. MR was found to be more sensitive than CT in the detection of areas of necrosis in the brain of the five children we studied. The absence of focal lesions detected by either modality in one of our patients did not exclude the diagnosis of SNE since focal lesions were present at autopsy one month following CT and MR.