The dynamic computed tomography (CT) study of the brain consists of the rapid i.v. injection of 49 ml of radiographic contrast material in 7 s followed by serial 5 s CT scans with interscan times of only 1 s. The data from these scans can be reprocessed to create 12 segmented images in 35 s. When small samples of 4-6 pixels of [baboon] cortex are examined by the cursor, sharp rises of 20-25 CT units (500 scale) are seen on the time-density curves. Samples of white matter are usually no more than 2 CT units. When larger cursor samples of 220-225 pixels including cortex and white matter are examined, the time-density curves represent a combination of these 2 patterns. Comparison between symmetrical areas in the 2 hemispheres generally shows parallel curves in controls. High resolution cerebral perfusion images are provided. In ischemia secondary to ipsilateral carotid stenosis, there is depression of the up-slope and a depressed and late peak. Infarctions show a flat perfusion curve. Several patterns in brain tumors are illustrated. The study, simple to perform, adds significant perfusion information to the previously static CT examination of the brain.