Atherosclerosis is the "hardening of the arteries" that contributes to heart attack, stroke and other cardiovascular disease. It involves the deposition of lipid into the inner lining of arteries, forming a atheromatous plaques full of cholesterol ("atheroma" comes from the Greek word for porridge, describing the consistency of the stuff inside the plaques). The plaques becomes hard (sclerosed) because of fibrous scar tissue and because of the deposition of calcium salts into them.

Atherosclerosis contributes to cardiovascular disease in at least three ways:

The effects of this arterial disease can be manifest in many ways. Obstructon of a coronary artery by plaque or platelet thrombus can give angina or heart attack. Platelet thrombi that break loose from a plaque in a carotid artery can travel (embolise) into the arteries supplying the brain, producing paralysis and loss of speech or vision that may be temporary ("mini-stroke": transient ischaemic attack or TIA) or permanent ("stroke": cerebrovascular accident or CVA). The large artery in the abdomen (aorta) can develop an aneurysm that ruptures, causing life-threatening internal bleeding. An artery supplying a kidney can partially block, causing the kidney to release hormones that increase blood pressure. The artery supplying a leg can be partially or totally blocked, giving cramping pain on exercise (claudication), or even gangrene.

The major risk factors for atherosclerosis are smoking (which doubles the risk), high cholesterol (which increases it by about one-half), diabetes, high blood pressure and age.

Once atherosclerosis is established it cannot be completely reversed. There is evidence that changes like stopping smoking and dramatically reducing cholesterol with drug treatment can allow some regression of the process.