Experience is reported of the use of immersion hypothermia on twenty-one occasions in seventeen patients in whom ethoglucid was injected by the intra-arterial route for the treatment of advanced cancer of the head and neck. The main hazards were found to be arterial hypotension occurring during the procedure and postoperative regional oedema leading to respiratory obstruction for which tracheostomy was required on eight occasions. The fall in white blood cell count was appreciably less than that reported after injection of comparable doses at normal temperature. The relief of pain after perfusion was marked.