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 016.4 to 11.0% and was 2.8 to 2.2% above control during stable distribution. In hypoperfusion, increase in attenuation was always below 10% in the arterial phase, while In hypoperfusion was characterized by an attenuation increase of 25 to 70%. Enhancement was defined by a density increase of 16.8 to 14.8% and a tissue blood ratio between and 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 recovers.