Full-body computed tomography (CT) screening came to Australia in 2002. Within a year, public access to self-referred full-body CT screening was withdrawn as a consequence of sustained professional and political pressure and legislative changes. We examine how self-referred full-body CT scans were made available to Australian consumers, and evaluate the social, cultural and system factors that contributed to their de-implementation. Using historical methodologies, insider accounts and an ethnographic content analysis of policy documents, statutory reports, grey and scholarly literatures, we show how the rapid de-implementation of full-body CT scans in Australia arose from interconnected social, cultural and system factors, and an unusual harm profile for the technology. In the Australian context, this case suggests that neither single actors nor robust health technology assessments are likely to be sufficient to protect people from the unwanted consequences of too much medicine. The coordinated interaction of multiple stakeholders achieved this unusual example of successful, early de-implementation. Each stakeholder exercised their authority within their respective remits to shape public perceptions of and access to the new CT screening service: it is possible that without the actions of each, the final de-implementation outcome may not have been achieved. These findings are timely, given growing concerns about overdiagnosis and the emergence of new forms of testing technologies. Against a background of technological optimism and commercial opportunism, a commitment to vigilance and cross-sectoral coordination across a range of decision-making roles and institutions will be key to efforts to prevent the harms of overdiagnosis.