We report the pathologic changes of the cardiac conduction tissue (CS) in 33 cases of sudden cardiac death. The cases were divided into two groups: those with severe atherosclerotic coronary lesion (> 75% cross-sectional area stenosis of at least one coronary artery), 15 cases, and those without significant coronary disease, 18 cases. In the first group, we observed major changes of the CS in eight cases. The changes consisted of abnormalities in His bundle position (branching bundle in pars membranacea or left-sided bundle), atrioventricular (AV) node fibrosis, and interatrial lipoma. Other age-related minor abnormalities such as mild fibrosis, fatty change, or fibrointimal hyperplasia of CS arteries were observed in nine cases. In the second group, major lesions of the CS were recognized in 13 cases: abnormalities in bundle branch position in eight cases (left-sided, inside the membranous septum), downward displacement of the tricuspid valve with AV node elongation in three cases, and a single case with one of the following: His compression by hypertrophic cardiomyopathy, Mahaim fibers, focal ischemia of bundle, AV node division, AV node dissection by edema, intramural left bundle branch, or tumor of the AV node. In the study of the pathogenesis of sudden death, the conduction system lesions always have to be considered, even in cases with severe coronary disease.