objective: Gamma Knife radiosurgey(GKRS) has proven effective and safe in critical and deep seated lesion of the brain where microsurgery cannot be accessed easily. It can provide effective alternative treatment modality particularly for geriatric patients. This study explored and evaluated the neurological disease and the treatment results of the geriatric patients who had received radiosurgery treatment. Matcrials and mcthods: This study reviewed the clinical outcome of 172 patients(72 male, 99 female) with ages 65 or older, who were part of 1241 patients who under gamma knife radiosurgery in our gamma knife center between march 1992 and December 2004. Mean age was 70.3 years old (range 65~86). 129 patients were available for follow-up observation with mean follow-up period of 18 monthes (range 3~48)s. Rcsults: Total 1241 Gkrs patients in our gamma knife center included 172 patients (13.9%) with ages 65 or older, Ninety two patients (53.5%) of them were diagnosed with benign brain tumors, 61 patients (35.5%) with malignant brain tumors, and 10 patients (5.8%) with functional disorder. The study also evaluated the proportion of geriatric patients in each neurological disease category to the total patients in the category. In the case of benign brain tumors, 92 patients (16.4%)  from total 562 benign brain tumors were elderly. In malignant brain tumors, 61 patients (20.1%) from the total 303 were elderly. In vascular disease, 10 patients (3%) of the total were the elderly. In trigeminal neuralgia, 9 patients (47.4%) of the total 19 were elderly. Of total cases of the geriatric patients evaluated, there 21 cases (12.2%) where GKRS procedure was performaed as secondary treatment on remained lesion or recurrent lesion after micorsurgery, and in the rest 151 cases (77.8%), GKRS procedure was performaed as an initial treatment.  With respect to radiosrugical dosimetry plan for bernign branin tumors, the mean volume of the lesions was 7.4cc(0.1-57.7) and the mearmarginal dose was 15.1 Gy (8~30) In metastatic brain tumors, the mean volume was 5.6cc(0.1~45.4) and the mean marginal dose 19.2 Gy(10~42). In vascular disease, the mean maximal dose of 78.1 Gy(74~82.5) was prescribed. The tumor control rate benign brain tumors was 95.8% and mean survival time of metastatic brain tumor patients after treatment was 17 months (range 8~22) In three cases, radiation induced complication occurred after GKRS treatment, Which was improved with following steroid treatment. Conclusion: Among geriatric patients with neurological diseases, gamma knife radiosrugery was performed most frequently for benign brain tumors, especially meningioma for which the treatment was performed the most in this category. Disoders that were treated with gamma knife radiosurgery in the highest percentage within given categories were metastatic brain tumor and trigeminal neuralgia. Results of this study indicate that Gamma Knife radiosurgery provides effecive and safe brain tumor control for geriatric patients. Further strdies utilizing more active follow-up the outcomes after GKRS treatment will provide more useful information of it's role in managenent in geriatric population