Most cerebral infarctions occur suddenly, some occur during activity, and some occur during sleep but are detected after waking up. There are many causes of cerebral infarction, but most patients have high-risk factors. The more recognized subtypes are atherosclerosis, and cardiogenic factors, such as heart failure and atrial fibrillation. Some patients have small infarcts caused by small atherosclerosis, and there are other cerebral infarcts of unknown origin. The causes of atherosclerosis include hypertension, diabetes, coronary artery disease and hyperlipidemia, so the usual primary and secondary prevention are the control of high-risk factors.