Radiotherapy is used to treat not only malignant tumors but also benign inflammatory and hypertrophic diseases. Because of concerns about the potential hazards of irradiation, physicians in many countries, especially in North America, ruled radiotherapy out of medical practice for non-malignant diseases. Low-dose radiotherapy modulates the inflammatory response, providing an anti-inflammatory effect. Many researchers have reported low-dose radiotherapy efficacious for degenerative and inflammatory diseases. There are broad potential clinical indications for radiotherapy of non-malignant diseases. The general indications for radiotherapy for non-malignant disorders are acute/chronic painful degenerative diseases, such as chronic or acute painful osteoarthritic diseases of various joints; hypertrophic (hyperproliferative) disorders of soft tissues, such as early stages of Morbus Dupuytren and Ledderhose, keloids and pterygium; functional diseases, such as dysthyroid ophthalmopathy and arteriovenous malformations; and others, such as prophylaxis of heterotopic ossification. Radiotherapy for non-malignant disorders may be safely and effectively used, especially in older patients who suffered from these disorders and those who are reluctant to use other treatment options.