Abstract: A catheter is adapted to exchange heat with a body fluid, such as blood, flowing in a body conduit, such as a blood vessel. The catheter includes a shaft with a heat exchange region disposed at its distal end. This region may include at least one balloon which is adapted to receive a remotely cooled heat exchange fluid preferably flowing in a direction counter to that of the body fluid. Embodiments including multiple balloons enhance the surface area of contact, and the mixing of both the heat exchange and the body fluid. The catheter can be positioned to produce hypothermia in a selective area of the body without cooling the entire body system. It is of particular advantage in brain surgeries where stroke, trauma or cryogenic tumors can best be addressed under hypothermic conditions.