Five cases of infarction in the territory of the middle cerebral artery (MCA) are reported. The main feature common to these 5 cases was the presence at CT without contrast injection, in the first 24 hours, of a spontaneous hyperdensity of the ipsilateral MCA. In one case, angiography demonstrated that this hyperdensity was associated with occlusion. In 2 other cases, doppler examination showed occlusion of the internal carotid artery. The transient character of these radiological findings is underlined. In the acute phase of an infarction, hyperdensity of the MCA at an early CT scan without contrast injection suggests an occlusive mechanism and massive infarction with poor clinical outcome.