Seventy-five patients with trigeminal neuralgia were treated by the injection of 0.2 to 0.4 ml of glycerol by the anterior percutaneous route into the trigeminal cistern, which was visualized by the aid of contrast medium (metrizamide). Eighty-six per cent of the patients were completely free from pain after the treatment, which produced only minimal disturbance of facial sensitivity. No complications have been observed. It is suggested that glycerol acts mainly on partly demyelinated nerve fibers, which are assumed to be involved in the trigger mechanism.