Benign neonatal seizures is a rare but increasingly recognized syndrome characterized by seizures in the neonatal or infantile period. Two forms are recognized: familial and nonfamilial. In both instances, the seizures may be quite severe, and status epilepticus is common. The nonfamilial form is characterized by idiopathic, self-limited seizures occurring in previously normal neonates. The seizures most commonly occur at day 5 and have been called "fifth-day fits" by some authors. Familial seizures most frequently have their onset during the first week of life, but onset may occur as late as early infancy. These seizures may recur for several months before resolving. No cause is found for the seizures, and the patient appears healthy during the interictal period. The family history reveals benign neonatal seizures in other family members. Although the prognosis is favorable in both syndromes, seizures may occasionally occur later in life in the familial form. The familial form of benign neonatal seizures is autosomal dominant, and the gene has been localized to chromosome 20.