Soon after its discovery in 1898, the potential physiological effects of radium, including its possible role in combating cancer, were recognised. Its therapeutic uses led to the founding of the Royal Dublin Society’s (RDS) Radium Institute in 1914, just 2 years after the establishment of the Institut du Radium in Paris. In tracing the history of the Institute and the use of radium therapy, this paper explores the role played by the RDS in the relationship between the emerging science surrounding radioactivity, the scientists that were promoting and developing this, and the pioneering medical professionals that sought to use this new science for the benefit of their patients in early twentieth-century Ireland. In doing so, it demonstrates that the Irish scientists and medical practitioners actively engaged with this new medical science, assimilating, contesting and reconstructing medical knowledge in a local context.