Clinical application of induced hypothermia for brain protection has expanded in recent years. There are many developments in laboratory and clinical investigations relevant to the relationship between neuronal death and brain temperature. Decreases in metabolic rate, tissue oxygen consumption, and energy demand most likely play less important roles in brain protection from ischemia, whereas more important possible mechanisms for brain protection include effects on excitatory neurotransmissions, intracellular calcium flux, membrane lipid peroxidation, free radical reactions, and permeability of the blood-brain barrier. Induced hypothermia has been applied to cardiovascular surgery and cerebral aneurysm surgery. In the intensive care unit, induced hypothermia has been applied to patients with traumatic brain injury, cerebral infarction, and subarachnoidal hemorrhage and after cardiopulmonary resuscitation. As hypothermia is not a physiological state, adverse effects would appear in cardiovascular, respiratory, coagulatory, immunological, metabolic, and other functions. Adequate indication, exact monitoring, temperature control, sufficient care, and an educated team are mandatory to maintain patient condition in a stable fashion and to avoid the complications associated with hypothermia.