OBJECTIVE: Cancer pain has been treated by gamma knife radiosurgery(GKS), targeted to the pituitary gland-stalk, as an alternative new pain control method. The purpose of this study is to prove the efficacy and the safety of this treatment. METHODS: Seven patients with intractable cancer pain underwent pituitary gland-stalk irradiation by gamma knife. Selections for patient inclusion in this treatment protocol were no other effective pain treatment options, general condition rated as greater than 40 on Karnofsky Performance Scale, and pain relief by morphine though not satisfactory. The target was the junction between the pituitary stalk and the neurohypophysis. The maximum dose was 150~160Gy with one isocenter in 8mm collimator or two isocenters in 4mm collimator keeping the radiation dose to the optic nerve less than 8Gy. RESULTS: In all seven cases, the significant pain reduction was obtained during immediate post-GKS period without serious complications except one patient who developed transient hypopituitarism and diabetes insipidus. Pain relief was observed within several days, and this effect was prolonged for a quite long time. At a follow up of 1.5 to 13 months, pain recurred in two patients and no hormonal and visual dysfunctions were observed. CONCLUSION: Despite insufficient experience, the efficacy and the safety of GKS for intractable cancer pain were demonstrated in seven patients. This treatment has the potential to ameliorate cancer pain, and GKS will play a more important role in the treatment of intractable pain.