The presence of a dense appearance of the horizontal part of the middle cerebral artery (the "dense middle cerebral artery sign") was looked for on CT scans taken on admission in 90 consecutive patients with ischemic stroke in the carotid artery distribution. The outcome of the 14 patients with the sign was poorer than that of 76 patients without the sign (Odds ratio 4.3). We suggest that this sign could be a useful prognostic variable in the acute phase of an ischemic stroke.