Valproate (VPA) is indicated for treatment of febrile convulsions (FC) and very infrequently is associated with impairment of cognitive functions. We present a 8 years old girl treated with VPA for FC who manifest a dramatic behavioral and intellectual disorder confirmed by neuropsychological tests. Three weeks after a reduction of VPA dosis we observed a spectacular clinical improvement. Then, medication was discontinued with normalization of the neuropsychological items, till now, more than one year later. At all time plasmatics levels of VPA were in range and we never observed direct toxicity by the drug. This is an exceptional picture, and for our knowledge never has been reported during treatment of FC. We think that is important to inform of drug-induced abnormalities like this for avoid unnecessary exams to search for neurodegenerative disorders.