A consensus on a quality assurance programme of the treatment of early breast cancer was reached in a multidisciplinary meeting of surgeons, pathologists, radiotherapists, physicists and radiographers. Guidelines for treatment preparation and execution have been set up, including careful location and excision with marking of the primary tumour. The target volumes for irradiation of the whole breast and boost area have been defined. Radiation dose prescription rules, specification and checking procedures are given, together with measures to achieve a homogeneous dose within the target volume. The rules for a quality assurance programme in each clinic are designed for checking equipment and treatment method. © 1991.