The term "radiosurgery" was defined by Lars Leksell, a Swedish neurosurgeon, as the closed-skull destruction of a precisely defined intracranial target using high-dose radiation with stereotactic technique in a single session. For this purpose, the Gamma Knife was developed in 1968. It was equipped with multiple cobalt 60 sources and delivered collimated narrow radiation beams precisely concentrated to the focus. The dose gradient in the periphery of the treatment volume is extremely steep, so a high dose can be delivered to the small target volume sparing the surrounding normal tissue. Treatment planning was directed using a computer program developed for Gamma Knife and stereotactically obtained imaging database. The treatment procedure may be completed in only one day. The Gamma Knife makes it possible to treat deep-seated and surgically inaccessible lesions with low mortality and morbidity, and to control conventionally radioresistant lesions. Up to now, over 10,000 patients have undergone radiosurgery with a Gamma Knife around the world. The indications were primarily functional disorders, then expanded to include arterio-venous malformation (AVM), benign and a few malignant brain tumors. Excellent results were noted in the treatment of AVM. The two-year total obliteration rate of the nidus was 71-87%, and the adverse effect rate was 3-12%. The control rates of acoustic tumors was reportedly 85-89% with a lower incidence of facial nerve injury and a higher rate of hearing preservation. Gamma Knife radiosurgery has also been used to treat meningioma, pituitary adenoma and metastatic brain tumors. Its application for the treatment of malignant glial tumors or other tumors is developing. The capability of this technique is growing, and radiosurgery will be one of the important treatment modalities for selected neurosurgical or other pathological conditions.