In 1987, the American Cancer Society has anticipated that 965,000 new cases of invasive cancer will be diagnosed in the United States. About 40% of those patients can be treated for cure with organ preservation using radiation therapy. The basic biologic background for such an approach to the problem has become well established. The clinical data to substantiate the validity of the concept date from 1902 until the present. Organ preservation has become a major and important concept in the management of the patient with invasive cancer. New and innovative techniques for treatment are enabling the organ to be preserved, the cancer to be cured, and appropriate cosmesis and function to be preserved. Many tumor sites are appropriate for this treatment technique, including breast, eye, larynx, prostate, soft tissue sarcomas, etc.