1. In radiation therapy for the control of abdomino-pelvic cancer, there is a calculated risk of serious injury to gastrointestinal viscera in return for the benefits of health.2. Serious injury to these vital organs can give rise to acute and long-term suffering, disability and even death. Several examples have been presented from our experience to illustrate the clinical pattern, life history and surgical management of these complications.3. Some of the technical and clinical factors which have a bearing on the frequency and severity of damage are carefully reviewed and analyzed.4. Guidelines are suggested for safer clinical practice to prevent or significantly modify the risk of serious early or late reactions.