In addition to the usual adverse effects, the chronic use of the valproic acid can entail dementia syndrome. We describe the case of a 68-year-old woman who had presented a dementia syndrome due to the use of valproic acid for one year. This drug was prescribed in order to prevent a potential convulsive crisis after an ischemic stroke in a patient who did not have a history of epilepsy. This case shows that each clinician must be careful about all medications consumed by the patient in the face of cognitive disorders.