A man underwent Magnetic Resonance Imaging (MRI) of the left carotid artery 11 days after a spontaneous dissection of this vessel. T1 weighed images were obtained in the frontal and axial planes. There was a hyperintense lesion expanding the arterial wall due to the hematoma. The image of the lumen was narrowed. These findings corresponded to the angiographic abnormalities. In this case MRI was able to diagnose specifically and non invasively carotid artery dissections. Its sensitivity remains to be evaluated.