Chronic cluster headache, also known as chronic migrainous neuralgia, is frequently unresponsive to medical management. Although neuronal factors may be involved in the pathogenesis of this form of recurrent hemicranial pain, vasodilatation within the distribution of the trigeminal nerve is believed to be important. Attempts to provide relief by surgical means have primarily involved interruption of the vasodilator pathways of the greater superficial petrosal nerve and the sphenopalatine ganglion. A more direct approach of interrupting the pain pathways of the trigeminal nerve has been attempted sporadically for more than 50 years. Recent interest in the role of substance P in the production of pain in cluster headache suggests that trigeminal ablative procedures might have a dual role in the relief of medically intractable cases. Among 26 patients who underwent posterior fossa trigeminal sensory rhizotomy or percutaneous radio-frequency trigeminal gangliorhizolysis at our institution, relief of pain was excellent in 14 (54%), fair to good in 4 (15%), and poor in 8 (31%).