The integration of nanotechnology’s ‘social and ethical issues’ (SEI) at the research and development stage is one of the defining features of nanotechnology governance in the United States. Mandated by law, integration extends the field of nanotechnology to include a role for the “social”, the “public” and the social sciences and humanities in research and development (R&D) practices and agendas. Drawing from interviews with scientists, engineers and policymakers who took part in an oral history of the “Future of Nanotechnology” symposium (...) at the Cornell NanoScale Facility, this article examines how nanotechnology’s ‘social and ethical issues’ are brought to life by these practitioners. From our analysis, three modes of enactment emerge: enacting SEI as obligations and problems-to-be-solved, enacting SEI by ‘not doing it’ in the laboratory, and enacting SEI as part of scientific practice. Together they paint a complex picture where SEI are variously defined, made visible or invisible, included and excluded, with participants showing their skill at both boundary-work (Gieryn Am Sociol Rev 48:781–795, 1983, 1999) and at integration. We conclude by reflecting on what this may mean for the design and implementation of SEI integration policies, suggesting that we need to transform SEI from obligations into ‘matters of care’ (Puig de la Bellacasa Soc Stud Sci 41(1):85–106, 2011) that tend to existing relationalities between science and society and implicate practitioners themselves. (shrink)