Persistent atrial standstill occurred in a father and his youngest son with familial Ebstein's anomaly. In both cases routine electrocardiograms showed no atrial electrical activity and cross sectional echocardiograms showed inferior displacement of the septal tricuspid leaflet and tethering of the tricuspid leaflets to the right ventricle. The father had a cerebral embolism and died of a myocardial infarction. Necropsy showed attachment of the septal tricuspid leaflet below the membranous septum. On serial histological examination fibrofatty infiltration of the right atrial wall, the atrioventricular node, and the inferior part of the His bundle up to the bifurcation was present. The son had haemodynamic and electrophysiological findings consistent with mild Ebstein's anomaly and persistent atrial standstill, for which permanent cardiac pacing was necessary. The persistent atrial standstill with slow escape rhythm was most probably a consequence of the abnormalities in both the atrial wall and the His bundle which, together with the abnormal attachment of the tricuspid valve, may be features of the same congenital cardiac anomaly.