The design and implementation of a computer-based training system for radiation oncology was undertaken. A frame-based system was chosen, with factual information from Principles and Practices of Radiation Oncology, by Perez and Brady, as the body of knowledge. Each unit of the system was based on a site (chapter) and consists of three sections: text, review questions, and patient management problems. The text section contains text, tables, and references and defines the information upon which the review questions and clinical cases are based. The review questions are multiple choice and true-false, and immediate feedback is given for both correct and incorrect responses. The patient management problems are interactive and provide alternative methods of presenting information and stimulating problem-oriented thought. The emphasis in all sections is on learning rather than testing. Advantages of a computer-based tutorial include the ability to present large volumes of information easily, the capacity for immediate feedback, and the flexibility of format in presentation of material. Potential applications are discussed.