The growing use of diagnostic X-rays and of high-dose techniques (CT, interventions) in children and adolescents is a topic of concern in radiological protection. Studies of other populations indicate that children are generally more sensitive to health effects of radiation than adults. In addition, children have a longer life-span to express any radiation-related health effect and, because of their smaller mass children, may receive higher doses to specific organs from these procedures if examination protocols are not adapted. Procedures of particular concern include: the use of CT in children (which delivers doses that are substantially greater than those from conventional X-rays); interventional cardiology, in which fluoroscopy is used to guide small instruments such as catheters through blood vessels (which, if repeated, can deliver doses of several hundred mGy to specific organs); and the use of repeated X-rays for monitoring respiratory, cardiac and digestive pathologies in premature babies (for repeated procedures, cumulative doses range up to a few mGy – and premature babies could be particularly sensitive to radiation induced diseases). Because the health effects of these low doses of radiation are expected to be relatively small, trans-national collaborative studies are needed to ensure sufficient statistical power to study these effects. In this project we seek support to assemble a critical mass of scientists involved in the study of medical radiation exposures and health effects of radiation dispersed throughout Europe with the aim of: ● Assessing the feasibility of establishing prospective trans-national cohorts suitable for long term follow up (including evaluation of the statistical power of the study) ● If the feasibility is demonstrated: - Making recommendations for future research needs including populations suitable for long term follow-up; - Developing specific project proposals, including study protocols and procedures for follow-up.