The passage of contrast medium was observed using serial computed tomography (CT) in 24 stroke patients. Density-time profiles of various brain regions were plotted. In normal brain tissue, X-ray attenuation showed a maximum increase during the arterial phase (16.4 .+-. 11.0%) and was 2.8 .+-. 2.2% above control during stable distribution. In hypoperfusion, increase in attenuation was always below 10% in the arterial phase, while hyperperfusion was characterized by an attenuation increase of 25 to 70%. Enhancement was defined by a density increase of 16.8 .+-. 14.8% and a tissue/blood ratio between 7-60%. An attempt was made to establish a relationship between the serial CT pattern and the prognosis. Enhancement tended to indicate severe morphological changes followed by permanent neurological deficit, whereas hyperperfusion was generally an indicator of probable recovery.