Devices and methods for warming or cooling blood flowing through thevasculature of a human or animal subject so as to alter or control thetemperature of all or part of the subject's body. Heat exchangers arepositioned within the subject's vasculature and heated or cooled heat exchangefluid is circulated through the heat exchanger. For certain therapeuticapplications, the heat exchanger and associated elements of the system havesufficient power to lower the subject's body temperature by at least 3 degreesC in less than 30 minutes.
