A stroke is a medical emergency and has to be treated immediately and efficiently. We differentiate between the haemorrhagic stroke which is caused by a brain haemorrhage and the ischemic one, which results from a restricted blood flow. We perform diagnostics with CT or MRI. As a stroke is related to the death of brain cells patients suffer from neurological impairments, such as speech or perceptual disorders or paralysis. Smoking, arteriosclerosis, high blood pressure and deviation of the heart rhythm are risk factors for stroke. Until 4,5 hours after the stroke the occluded artery can be treated with medication to facilitate the normal blood flow. Such critical care for stroke patients can be provided in acute stroke units.