The papers in this special edition are based on contributions to the symposium “Trustworthy nanotechnology” in Trondheim, Norway in June 2010. This symposium was initiated by the research project NANOTRUST,1 funded by the Research Council of Norway’s Programme for nanotechnology and new materials. The motivation for the project was a realization that the question of trust in nanotechnology has been raised at a stage when the material, conceptual and social body of nanotechnology has been in its infancy. As trust or distrust in social and technological systems generally is based in previous experiences with these systems, nanotechnology raises new conceptual and social challenges. A number of public engagement exercises and research projects on the societal aspects of nanotechnology have, due to the relative novelty of the nano field, been fairly general in their involvement with the technology. One of the potential strengths of this project was its collaboration with a project investigating the use of polymeric micro- or nanoparticles to enhance vaccine formulations for farmed salmon. Thus we raised the question of trust in relation to a concrete case of nanotechnology development, integrating ELSA research with the technology research. Reflecting on trust in collaboration with technologists at this early stage has both advantages and drawbacks. It provides a unique opportunity in creating a forum for ethical reflection, opening the possibility for making a positive impact on technology development. By engaging technology researchers at this stage one can avoid the historical role of ELSA research as an exercise in negative ethics, i.e. ethics as border guard against real and perceived risks and harm to environment and society. On the other hand, being too far upstream may imply that the engagement is reduced to hypothetical discussions or conceptual clarifications. Engaging with nanotechnology at this stage means that attempts to foster public trust would need to focus less on technological products and more on the complex process of science. While a products focus draws attention to the public’s choices, understanding, knowledge and acceptability of the product, a process focus draws attention to the visions and goals as well as organization and governance of nanotechnology. Thus the focus of the project and the symposium shifted from the conditions for public trust in general, to the body of scientific practitioners and practices that is to be trusted. This shift implies a corresponding shift from the concept of trust to the concept of trustworthiness and from what conditions trust to what conditions trustworthiness. With this focus, we aim at addressing to what extent nanotechnology is providing a sound basis for fostering public trust. One important feature of recent approaches to technology studies is that they draw attention to extraordinary cases where there is much at stake, values are disputed and high risks are involved. These cases are often accompanied with high degree of controversy, either scientifically or publically, calling attention to post-normal strategies that widens the circles of engaged stakeholders. Controversies function as a mobilizing factor. The normal case however is not the one of controversies, but more like the case of exploring PLGA particles for delivery of vaccines in aquaculture. Projects like this one, that run under the heading of nanotechnology display low degree of substantial controversy. When the mechanisms of society “talking back” to science [3] are staged through initiatives like the NANOTRUST project there is little visible and unusual scientific or public questioning—neither of individual projects of nanotechnology nor of nanoscience initiatives in general. Nanoscience and -technology differs from genomics in this respect: the “talking back” is staged in ways that may suppress internal scientific conflicts, conflicts on specific products, engage NGOs or media coverage in the ways that we have witnessed in connection with genomics. Therefore the symposium sought to explore how the challenges related to trustworthiness can be raised in projects where there are few or no controversies to spark increased scrutiny and scientific self-reflection. What do such normal cases require from the working scientist in terms of their responsibility to display and be able to normatively account for co-produced societal changes? How can and should nanotechnologists meet the challenge of societal interaction under such presumably low risk circumstances? In this issue, three of the papers are products of the reflections of the NANOTRUST research group on the trustworthiness of a technology application subject to uncertainty and ignorance regarding potential harms to health and environment. In addition, we include papers related to two of the invited presentations that contextualized the issue of trustworthiness based on other nanotechnology governance research projects.