The potential risks associated with radiation exposure from medical imaging have received considerable attention in the media recently. In a desire to improve safety, efforts to reduce radiation exposure to appropriate levels are being made by organizations and facilities across the country and the world. But what is the “appropriate” level of radiation for a given examination? In fact, what is the national average level of radiation that is currently being administered by imaging facilities for a particular examination, for example, a CT scan of the head? The answer to this question is not known; but this is precisely the type of question for which the ACR Dose Index Registry (DIR) soon hopes to provide insight. The DIR is part of the ACR’s National Radiology Data Registry (NRDR), an information system that provides accurate and objective measures of practice processes and outcomes. Like other registries that are part of NRDR, the DIR will allow facilities to compare their CT dose indices to peer facilities and national values. The development of the registry has been a lengthy process requiring solutions to a variety of problems, including the standardization of procedure names and data elements, patient privacy, legal issues, technological issues, and vendor competition. Having overcome these hurdles, the ACR intends to launch the DIR in 2011.