Familial neonatal seizures are an important and probably underrecognized disorder. A family with six affected individuals in three generations was evaluated and their clinical characteristics were compared with those of 15 families previously reported in the literature. An analysis of the 116 affected individuals uncovered a typical clinical picture of onset of seizures by 2 to 8 days of life in an otherwise healthy appearing infant, and cessation of seizures by 1 to 6 months. Results of diagnostic evaluations were normal, and the pathogenesis of the disorder is still unclear. Long-term neurodevelopmental outcome was normal except for an increased rate (11%) of subsequent seizures in childhood or as an adult. The disorder was inherited as an autosomal-dominant trait with a high degree of penetrance.