In autopsy files from April 1999 to April 2001, five cases showed macroscopic subendocardial small infarct above 1 cm diameter in the superior ventricular septum (SVS) near the atrioventricular (AV) junction, and all five were finally considered to be sudden cardiac death after full investigation. All these small infarcts in these Japanese patients were located at the posterior site of the SVS, an area mainly nourished by branches which ramified from the AV node artery and which branched from the right coronary artery (RCA). Four of the five showed acute (A) or subacute (SA) foci in or around the healed (H) lesion and surviving myocytes were visible in infarcts, in all cases, which suggested a recurrent or chronic prolonged ischemia in the territory. Four of the five had a significant stenosis of the RCA and in the other one, there was an anomalous origin of the RCA. As all five had also small artery disease in the SVS, small infarct of the posterior SVS may have formed by hemodynamic impairment in the territory of the AV node artery caused by RCA disorders. We consider the evidence of macroscopic small infarct of the posterior SVS greatly aids in determining the cause of sudden death in forensic autopsy and may be notable lesion for discussing the pathogenesis of sudden cardiac death with RCA disorder.