Twenty-nine patients with massive ischemic stroke (MIS) admitted to the hospital in the first 12h after stroke were examined. On the primary CT scan, there were no zones with decreased density of brain matter. A subsequent CT was performed on the next day to visualize stroke lesions. Correlations between the density of the trunk of the middle cerebral artery (MCA) on the primary CT, the volume of the lesion on the subsequent CT and the character of disease course were analyzed. It was shown that the CT-sign of MCA trunk thrombosis in the acute stage of MIS is a highly-specific predictor of MIS but a less effective predictor of an unfavorable benign disease course.