Background: There are few reports describing the features of maternal anti-SSA antibody-associated congenital complete heart block (CCHB) patients developing endocardial fibroelastosis (EFE). The aim of this study was to describe the clinical features and the outcome of patients with CCHB, with or without EFE. Methods and Results: Over a 20-year period, 12 consecutive patients diagnosed with maternal anti-SSA antibody-associated CCHB were identified. The maternal anti-SSA antibody levels were measured and fetal echocardiographic findings were reviewed. The ratios of the thickness of the endocardium to that of the whole wall of the left ventricle (LE/W) and right ventricle (RE/W) were measured to investigate the degree of endocardial thickening. A total of 7 patients survived (living group) and were not diagnosed as having EFE. The remaining 5 patients died and were diagnosed with EFE during autopsy (dead group). Fetal echocardiography of the patients showed differences in the thickening and hyperintensity of the endocardium. The RE/W value was significantly higher in the dead group than in the living group. The titers of both maternal anti-52-kDa and anti-60-kDa SSA antibodies were high, but showed no significant differences between the 2 patient groups. Conclusions: EFE was the major negative prognostic factor for CCHB. Myocardial damage, predominantly in the right ventricle, was related to the outcome of CCHB associated with EFE. (Circ J 2011; 75: 1215-1221)