Thesis (MScEng) -- Stellenbosch University, 2003. / INTRODUCTION: The Medical Radiation department at iThemba LABS provides proton beam therapy facilities for irradiation of intracranial, head and neck lesions. Proton radiation treatment offers a number of advantages over alternative radiation therapy modal- ities. The most significant advantage is the ability to localize the dose to the lesion or target volume [16]. Lesions are located by means of medical imaging processes, such as Computer Tomography (CT) or Magnetic Resonance Imaging (MRI) scans. Patient treatment commences at the existing treatment facility of iThemba LABS. The patient positioning system that is currently in use at this facility was designed for only one horizontal beam delivery system and a limited number of treatment positions. The possibility of acquiring an additional beam delivery system and im- proving the utilization of the system resulted in plans to expand the current proton therapy capabilities. These plans resulted in the development of a new treatment vault, complete with a new patient positioning system. The new vault will cater for two beam delivery systems and expand current treatment positions.