We found a DE NOVO missense mutation of the gene encoding the alpha1 subunit of the neuro-nal voltage-gated sodium channel, SCN1A, in a patient with repetitive focal seizures. At 5 months of age, the patient had a first seizure characterized by loss of consciousness and clonic convulsions in the left hand followed by secondary generalization lasting for 20 minutes in association with pyrexia. Although valproate was administered, she has had generalized seizures every month, mostly in association with elevated body temperature. Since 32 months of age, she also had a different type of seizure characterized by a fearful response followed by decreased consciousness, pallor, and salivation. Myoclonia or atypical absence seizures have never been observed until the last follow-up at 42 months of age. Genetic analysis showed a heterozygous missense mutation (c.5311A>T: I1771F) in the patient, which was not detected in her parents.