Serial computerized tomography (CT) was performed to quantitatively characterize cerebral changes in 1 case of the interval form of carbon monoxide poisoning. The patient was comatose for 2 days, regained consciousness for 8 days, and then developed akinetic mutism. During the remission period, a low-density area in the cerebral white matter was observed to enlarge progressively. These results suggest that the demyelination of the cerebral white matter progressed throughout the interval period. A correlation between changes in CT abnormalities and clinical presentation is described.