In this paper we have tried to explain the natural history of atherosclerosis as a condition marked by intimal vessel expansion tending to the endoluminal proliferation until to the obliteration of the lumen because of the presence of atheroma with fixed stenosis. During the course of the life, the various histologic alterations are responsible of the different ischaemic syndromes, ranging from instable vasospastic angina, to chronic ischaemia caused by fixed stenosis, until to myocardial infarction. Besides, we have outlined that in the young (< 40 years old), the most frequent and important event is the vasospasm owed by the fibromuscular proliferation that could cause an infarction with "intact" coronary arteries. On the other side, in the elderly, are observed specially degenerative atherosclerotic lesions with fixed stenosis and consequent thrombosis, cracking of the plaque as cause of acute myocardial infarction.