The pathophysiology of acute coronary syndromes is characterized by an acute mismatch of blood supply to the myocardium to meet the prevailing metabolic need. By far the commonest aetiology of myocardial ischaemia is coronary artery disease . An inflammatory process that evolves over the period of many decades, coronary artery disease is characterized by the deposition of cholesterol and cholesterol laden macrophages within the intima of the vessel wall. This process can be accelerated by a number of cardiovascular risk factors (smoking, hypertension, hyperlipidaemia, hypercholesterolaemia, diabetes), which can culminate in the formation of the unstable plaque responsible for the emergent presentation of ST-elevation myocardial infarction. This chapter reviews the prolonged inflammatory process responsible for atheroma formation, along with rarer, non-atheroma-related causes of acute coronary syndromes.