The successful application of radiotherapy requires the active participation of the physicist in a multidisciplinary group including radiation oncologists and radiation therapists. The detailed role of the physicist varies from place to place but the following core activities can be identified. 1) as a member of the team to prepare specifications and select new equipment, to advise on equipment layout and on matters concerning radiation protection, and to perform acceptance tests on the new installation; 2) to undertake commissioning measurements including beam calibration and the measurement of all dosimetry data required for treatment; 3) the physicist is required to ensure that the radiation, to be used for patient treatment, will have been fully characterised so that the radiation dose prescribed will be delivered to the tumour volume. This implies being responsible for the maintenance of the treatment unit and other associated equipment either directly under the physicist's own supervision or indirectly; the physicist should monitor equipment performance and its continued suitability for the clinical purpose; 4) to be responsible for all dosimetric measurements, calibrations, etc.; 5) commonly to take overall responsibility for treatment planning and always to have an essential role in the development or implementation of new treatment techniques, the selection and quality control of treatment planning systems, and the control of treatment planning data; 6) to be responsible for the supply, safe keeping, preparation and dosimetry of sources used for unsealed and sealed source therapy. Whilst including all of the above, the specific objectives of the physics section in this department involve the following: · preparation of and calculation of dosimetry for eye plaque treatment; · preparation of and calculation of dosimetry for high and low dose brachytherapy; · maintain a highly efficient computer network; · oversee the physics workshop; · assist with and suggest student projects for medical physics students; · lecture oncology registrars on radiotherapy physics; · liaise between oncologists and therapists in matters related to patient treatment; · maintain radiation protection for POWH, PHH, The Womens Hospital and South Sydney.