A family in which several members of three separate generations have evidence of congenital familial conduction disturbance has been described. The occurrence of Adams-Stokes seizures with congenital AV block was also noted. From the available information it is clear that the conduction disturbance was congenital in two generations, and the family history suggests that three or four generations were probably involved. The data suggest that in this family the congenital cardiac conduction defects were transmitted as an autosomal dominant trait with incomplete penetrance.