Therapeutic hypothermia (TH) improves the neurological outcome in experimental brain trauma models as well as in patients suffering from cardiac arrest and perinatal asphyxia. So far the efficacy of TH has not been proven in acute ischemic stroke due to lack of clinical data. The EuroHYP-1 study will investigate whether TH with an individual target range temperature between 34 and 35 °C administered for 24 h will improve the neurological outcome in ischemic stroke patients treated within 6 h from symptom onset. The target patient number of 1,500 to be included in EuroHYP-1 is sufficiently powered to detect the efficacy of TH.