Nine progressive supranuclear palsy (PSP) patients were studied with computerized tomography (CT) and magnetic resonance (MR) in order to determine the efficacy of each in detecting atrophy of the brainstem. Three additional PSP patients were evaluated with MRI for quantitative (electronic) measurements of the colliculi, pons and midbrain tegmentum. Both CT and MRI were equally effective in demonstrating midbrain atrophy. The MR was able to utilize the sagittal view to visualize thinning of the collicular (quadrigeminal) plate, a useful sign in PSP. Atrophy of the thinned collicular plate is more pronounced in the superior colliculus, one of the most common sites of pathology in PSP. The MR is able to make quantitative measurements of the degree of atrophy of the colliculi, pons and midbrain tegmentum.