In April, 1994, the American Association of Physicists in Medicine published a ``Comprehensive QA for radiation oncology:`` a report of the AAPM Radiation Therapy Committee. This is a comprehensive QA program which is likely to become the standard for such programs in the United States. The program stresses the interdisciplinary nature of QA in radiation oncology involving the radiation oncologists, the radiotherapy technologies (radiographers), dosimetrists, and accelerator engineers, as well as the medical physicists. This paper describes a comprehensive quality assurance program with the main emphasis on the quality assurance in radiation therapy using a linear accelerator. The paper deals with QA for a linear accelerator and simulator and QA for treatment planning computers. Next the treatment planning process and QA for individual patients is described. The main features of this report, which should apply to QA programs in any country, emphasizes the responsibilities of the medical physicist. (author). 7 refs, 9 tabs.