Four men and two women were treated for refractory cluster headache by gamma knife radiosurgery of the trigeminal nerve root entry zone. The maximum dose of radiation was 70 Gy to the isocenter. Of five patients treated who had refractory chronic cluster headache and one with refractory episodic cluster headache, four had relief judged excellent. Of the two remaining patients with refractory chronic cluster headache, one had relief judged good and the other fair. Five of the six patients treated had relief within a few days to a week following gamma knife radiosurgery. Three with chronic cluster headache had remissions allowing cessation of all preventive and abortive medication. Although one patient experienced complete relief of chronic cluster headache, he continued to have migraine requiring medication. None of the patients treated developed significant postradiation side effects during a follow-up period of 8 to 14 months. The authors conclude that gamma knife radiosurgery of the trigeminal nerve affords great promise in the management of chronic and refractory cluster headache. The technique seemingly carries negligible short- and long- term risk.