The authors report on a 37 year old right-handed patient with a right rolando-parietal infarct which was manifest clinically by not only sensory-motor disorders of the left side of the body, but more especially by an expression aphasia. This observation fulfills the criteria for defining the exceptional case of crossed aphasia in a right-handed patient: aphasic destruction of language engendered by a right unilateral lesion in such a patient, without a previous history of a cerebral lesion or family history of left-handedness. Comparing the aphasic signs in this patient with the rare cases reported in the published literature shows that there is a particular pathognomonic profile, close to the type of aphasic disorganization seen in children and left-handed adults. The authors review the neuropsychopathogenic explanations for this crossed aphasia of right-handed patients.