The case of posttraumatic patient with persistent vegetative state and severe and prolonged hyperthermia (T = 39-40 degrees C for more than 20 days), in absence of infection, is described. Diffuse muscular rigidity, treated with L-dopa, slightly preceded the onset of hyperthermia, which was treated with several antipyretics, including phenotiazines. The withdrawal of these drugs and the administration of dantrolene and bromocriptine was followed by the restoration of the normal body temperature.