We have developed a novel method of brain surface dialysis that reduces intracranial pressure and modifies movement of extracellular fluid in a rat model of brain injury. A chamber with a semipermeable membrane at the site of brain contact is perfused with a hyperosmolar solution (e.g. 15% dextran, inulin, hydroxyethyl starch). It is also capable of providing local brain cooling. In principle, osmotic forces draw water and small molecules from the injured brain into the dialysis chamber thereby reducing brain swelling. The dialysate does not move into the brain.