Emerging nanotechnologies pose a new set of challenges for researchers, governments, industries and citizen organizations that aim to develop effective modes of deliberation and risk communication early in the research and development process. These challenges derive from a number of issues including the wide range of materials and devices covered by the term 'nanotechnology', the many different industrial sectors involved, the fact that many areas of nanotechnology are still at a relatively early stage of development, and uncertainty about the environmental, health and safety impacts of nanomaterials. Public surveys have found that people in the United States and Europe currently view the benefits of nanotechnologies as outweighing their risks although, overall, knowledge about nanotechnology remains very low. However, surveys cannot easily uncover the ways that people will interpret and understand the complexities of nanotechnologies (or any other topic about which they know very little) when asked to deliberate about it in more depth, so new approaches to engaging the public are needed. Here, we report the results of the first comparative United States-United Kingdom public engagement experiment. Based upon four concurrent half-day workshops debating energy and health nanotechnologies we find commonalities that were unexpected given the different risk regulatory histories in the two countries. Participants focused on benefits rather than risks and, in general, had a high regard for science and technology. Application context was much more salient than nation as a source of difference, with energy applications viewed in a substantially more positive light than applications in health and human enhancement in both countries. More subtle differences were present in views about the equitable distribution of benefits, corporate and governmental trustworthiness, the risks to realizing benefits, and in consumerist attitudes.