We report on an autosomal dominant neonatal-infantile seizure disorder and offer criteria for establishing the diagnosis and guidelines for the evaluation and treatment of this disorder. Long-term anticonvulsant treatment usually is not required. The subsequent risk of a recurrent seizure disorder depends on whether other affected relatives developed a seizure disorder later in life. This disorder may have at least two different neonatally indistinguishable forms: one having an increased empiric risk (20%) of subsequent epilepsy, and a second which carries no increased risk. These familial neonatal-infantile seizures are termed "benign" since they are not associated with subsequent psychomotor retardation.