The European Union encourages and institutionalizes participation by environmental, consumer, and labor organizations in the governance of nanotechnology. Interviews with leaders of the civil society organizations (CSOs) show that they identified multiple problems with nanotechnology policy but had only limited success in gaining the changes that they sought. CSO leaders explain their lack of success as due to the overwhelming power of industry and the support of the European Commission for new industrial development, including nanotechnology. We analyze the perspectives of CSO leaders about their difficulties to develop the theory of the political opportunity structure in the situation of a highly scientized policy field with strong industrial monitoring. We suggest the need to extend the theory to pay more attention to the strategies that reformers can use to maneuver in and to open a relatively closed political opportunity structure. We argue that formal stakeholder engagement is not very effective and suggest instead the importance of the following: building coalitions with government actors, threatening or mobilizing grassroots mobilization, making the issue salient to the public, and pursuing the full range of institutional repertoires.