The only radiotherapy facility in Guyana, located at Cancer Institute Guyana (CIG) has a linear accelerator (LINAC), potential to produce photons of 6 Megavolts and 6 electrons energies of 5,7,8,10,12 and 14 MeV. This research aims to evaluate the levels of ionizing radiation retrospectively received by the OEP in the radiotherapy facility at CIG for 5 consecutive years from 2010 to 2014 inclusively and to relate the findings to the national and international dose limits of 20 mSv/year, for both safety and regulatory purposes to avoid and/or reduce biological effects. The Occupationally Exposed Personnel (OEP) are routinely monitored by the quarterly genesis Ultra TD dosimeter authorized by Sierra Radiation Dosimeter Service. Even though the results were well below the National and International dose limit, the results produced a variation of more than 2.1 mSv with a minimum mean annual dose of 0.264 mSv and a maximum mean annual dose of 2.353 mSv. Each OEP dose readings throughout the years was significantly below 5 mSv/year. These results allows the researcher to conclude even though the dose is well below 20 mSv, the need for optimization still applies. Background radiation, cannot be removed completely, but continuous monitoring should be done to help keep allows for radiation dose As Low As Reasonable Achievable (ALARA).