Five patients afflicted with subacute sclerosing panencephalitis were studied with computed tomography and magnetic resonance imaging. Computed tomography documented changes of nonspecific cerebral atrophy and low attenuation in the subcortical white matter. Magnetic resonance imaging revealed bilateral, symmetric, and diffuse abnormal increased signal in the white matter of the cerebral hemispheres with normal posterior fossa structures in 4 of 5 patients. Magnetic resonance imaging was superior to computed tomography in demonstrating the total extent of abnormality and may be the imaging modality of choice for this childhood disease.