Controlled medical terminologies that have been developed to describe terms utilized in the field of Radiation Oncology, include SNOMED-CT and DICOM-RT. However, a literature review has failed to provide evidence that the coverage and the level of granularity of these nomenclatures have satisfied the needs of radiation oncologists. Indeed most investigations conclude that the coverage is generally unsatisfactory. Fur-thermore, there is no evidence that an objective specification of the specialist medical terms used in Radiation Oncology has been developed. We report the development of a Specialist Medical Vocabu-lary for Radiation Oncology using an objective and systematic method of discovery of data elements published in the Radia-tion Oncology literature. The importance of the data elements to radiation oncologists is judged according to the criterion that a submitted report has been deemed worthy of publica-tion. Within the time period of discovery, 97 articles were retrieved and, during the analysis of 80 articles, 622 individual data elements and 2392 instances of use were found. Infrequent data elements comprised the majority of individual data elements (54%), and frequently used data elements were a minority (27 individual data elements with 10 or more in-stances of use). However these 10 data elements comprised 49.5% of the total data elements found.