Life scientists have increasingly been asked to incorporate a dual use responsibility in their research conduct. In this thesis, different aspects of what constitutes a reasonable responsibility in terms of avoiding harmful misuse of research for biological weapon purposes have been explored. The first study investigated the claim that scientists have a dual use responsibility, and also outlined some of its possible content. Criteria for what may constitute preventable harm were used to analyze some proposed obligations in the field, and it was concluded that reasonable obligations include: e.g. considering the potential negative implications of one’s research and reporting activities of concern. In the second study, the conditions for a Precautionary Principle (PP) were explored and applied to the dual use research context. The study found that the main conditions of the PP frequently appear in present discussions and formulations of life scientists’ responsibility. It was also concluded that the PP is applicable to the dual use field and that it is meaningful and useful as a normatively guiding principle. The third study suggested an ethics of dissemination, based on the assumption that scientists have a responsibility to occasionally constrain the dispersion of their research findings. Three core aspects were proposed for an ethics of dual use dissemination. Additionally, to help scientists understand when constraints may be justified, three corresponding conditions for their application were suggested. In the fourth study, the concept of ethical competence was introduced and explored within a dual use context. It was concluded that competence-building is important in the nurturing of individual responsibility and, subsequently, in achieving a culture of dual use responsibility in the life sciences. Finally, the discussion on ethical competence was included in a proposed ethic of deliberation, in which various stakeholders in the dual use debate are conceived to participate in communicative processes. It was argued that spaces for deliberative activities should be institutionalized by the scientific community to ensure structural opportunities for individuals to both assume responsibility and share it. Moreover, it was argued that deliberation can constitute a cornerstone of responsible dual use governance.