Body temperature below 35oC is defined as hypothermia. It is classified as mild, moderate and severe. While the standard thermometers can not measure the core temperature below 35oC, thermometers with intravezical, rectal or esophageal probes must be used to determine the core temperature in hypothermic patients. Although hypothermia is seen in cold climates; it can be seen because of environmental conditions, like drowning, too. Also inadequate clothing and hypothermia background can facilitate hypothermia in patients. The common causes for hypothermia are dermatological disease, drug adverse effects, iatrogenic causes, neurological disease, neuromuscular insufficiency, sepsis and metabolic condition of the patient. Resistance to cold in the peoples is not well developed while they are warm-blooded. Especially homeless, psychiatric and old alone peoples can be affected by hypothermia easily. Although the main heat loss of the body is by radiation; conduction, convection and evaporation take place too. Coordination and consciousness deficiencies are the main symptoms. Nevertheless clinical signs vary according to the hypothermia state. The basic treatment principles resemble each other in mild, moderate and severe hypothermia. These are; reducing of the heat loss, warming of the body with internal and external ways, supplying the main energy and fluid demands for patient metabolism. The defibrillation techniques, resuscitation time and the drugs which are used are different in hypothermic cardiopulmonary resuscitation than normal cardiopulmonary resuscitation. The main systems which are damaged from hypothermia are cardiovascular and central nervous system. That’s why early and true diagnosis and aggressive treatment has a great importance for surviving.