We examined family pedigrees of children with severe breath-holding spells (SBHS). There were 57 probands (27 males, 30 females; 44 cyanotic, 13 pallid) whose families comprised 1683 individuals. We found that 31 (27%) of 114 proband parents and 9 (21%) of 43 proband siblings had current or prior SBHS. Father-to-son transmission was observed in 7 instances. There were 7 families with 2 or more affected siblings and 5 families with 3 or more affected members. From 85 nuclear families, 130 individuals had current or prior SBHS (59 males, 71 females; male/female ratio, 1:12). These data suggest that the most likely underlying genetic inheritance pattern in SBHS is an autosomal dominant trait with reduced penetrance.