For seven years before admission to hospital on 6.3.70, a 52 year old man had several episodes of "fainting" but no chest pain. Investigation showed a slow pulse, but no evidence of myocardial infarction. BP 200/170. A diagnosis of coronary insufficiency was mad. For three years, he had been treated for high blood pressure, and for three months, had suffered chest pain on exertion. For the week prior to admission he had had chest pain at rest, and the pain had been persistent for five hours before admission. On examination, pulse 66/minute, BP 150/110. Investigations showed myocardial infarction. He appeared to be improving, but had a sudden cardiac arrest and died 15 days after admission. There is extensive infarction of back wall of the left ventricle involving the whole thickness of the wall. The infarct extends from the junction with the atrium to within 10 mm of the apex. The central part shows yellow dead muscle, and bordering on this is a narrow greyish zone of early scarring. The right coronary artery has been dissected and shows portion of the thrombus, which originally extended for 40 mm, commencing 10 mm from the origin of the vessel. The infarct is estimated to be approximately 2-3 weeks old.