A case is reported of a 56-year-old man with primary coronary dissection presenting as sudden death due to aortic rupture and cardiac tamponade. He was admitted because of loss of consciousness and chest pain. ECG showed complete atrioventricular block and myocardial infarction. Coronary angiography demonstrated coronary dissection and total obstruction of right coronary artery (RCA). Intracoronary injection of urokinase was not effective for recanalization of RCA. He died suddenly two days later. At autopsy, the proximal site of the ascending aorta was dissected locally and had ruptured into a pericardial space. RCA was torn off. The perivascular area around the torn coronary artery communicated with the dissecting space of the ascending aorta. Histologically, no degeneration or infiltration of inflammatory cells was observed in the media of the aorta and the right coronary artery. Histological change was observed only at the media of the torn site of the coronary artery. The thickness of the media was about half of that at the other site of the coronary artery. This is the third case reported in world medical literature of primary coronary dissection presenting as cardiac tamponade.