This thesis is concerned with the definition of radiobiology by the Medical Research Council (MRC), the state financed medical research funding organisation, in inter-war Britain. It argues that radiobiology was largely .. defined as a specialty by struggles in surrounding fields - particularily radiology, clinical research and the bio-medical sciences. Groups within each of these fields turned to experimental research into the biological effects of radiation to further their attempts to secure an autonomous professional space within medicine, often against resistance from the leaders of medical practice. The MRC was crucial to these attempts, as it provided the first and major systematic research programme into the medical uses and biological effects of radiation during the inter-war years. However, I argue, experimental research was generally subverted to clinical objectives. Indeed, experimentalists themselves were uneasy about clinical domination of their research. However, they were farced into alliance with clinicians partly because they required a medical justification for using the Council's small supply of radium, and partly because the Council's independence in medical research was threatened by the leaders of medical practice. If the Council was not the ideal place to foster experimental research free from clinical interference, the clinicians who dominated it were also opposed to the control of research by the leaders of medical practice, and were generally mare sympathetic towards the bio-medical sciences. Con~equentlYI mast experimental scient~sts sided with these clinicians in order. to protect the Council's independence. Radiobiology reflected the accomodations each side had to make in this alliance.