A stereotactic body frame for exact tumor localization, reproducible fixation, and high-dose fraction irradiation with an accelerator (radiosurgery) has been developed. With the aid of this body frame, tumors are usually treated with five to nine static coplanar or noncoplanar beams yielding a planned inhomogeneous dose distribution with a 50% higher dose in the center of the tumor compared to the periphery of the planning target volume. Due to the steep dose gradient, the surrounding normal tissue is exposed to relatively low doses. Seventy-five evaluable tumors in 50 patients in whom conventional treatment modalities had been exhausted or considered inapplicable have been treated with doses of between 15 and 45 Gy (mean, 28 Gy) at the periphery of the planning target volume delivered in one to five fractions (mean, 2.5). The tumors, which had volumes ranging from 2732 cm (mean, 73 cm'), were mainly metastases, from a variety of primaries, in the liver, lungs, and retroperitoneal space. Some primáries such as lung cancer and primary liver cancer were also treated. During an evaluation period of 1.5-38 months (mean, I 1 months) 22 tumors showed growth arrest (29.3%), 29 were reduced in size (38.7%), and 24 děsappeared (32%) as judged by computed tomography examinations, which were usually performed at 2- to 3-month intervals afier radiosurgery. Four of the tumors were classifica as local failures (5.3%). This treatment, which is noninvasive, painless, and rapid and does not require hospitalization, does not impair the quality of life of the patients when used properly. Treatment has been given regardless of age and medical status of the patients