This article examines corporate participation in the UN Global Compact programme. Using data on the world's 2,000 largest companies, we address the question of why companies voluntarily assume the programme's responsibilities and promote the rights of ‘global citizenship’. Our analytic approach is to view transnational corporate political behaviour as a result of firm-level decisions shaped by country-level variation in political audience effects. Drawing on earlier research on more conventional forms of corporate political activity, we expect factors influential in the standard model of firm political activity to determine participation in the Global Compact. In addition, we argue that this highly visible, less instrumental dimension of a firm's political behaviour is driven by efforts to build a good environmental and human rights reputation with its audience of external actors. The importance of environmental and human rights concerns depends on the substance of the firm's business activities, the availability of investment and ‘exit’ options, and the home audience's bias towards the UN and human and environmental rights. We find support for political factors as well as firm and industry-level characteristics influencing the decision to participate in the Global Compact.