We live in a world in which ever-greater arenas of social life are shaped by standardization and bureaucratic rationalization, as the pursuit of ‘measurable results’ sweeps everything from universities to hospitals to international organizations. Yet intuitively we understand that much of our collective and individual existence escapes these efforts of rationalization. How then do we develop a conception of the social world that appreciates both the powerful drive towards rationalization and the things that escape or overflow? This article seeks to answer this riddle by examining the central role of ambiguity in social life in general – and in organizational practice in particular. The concept of ambiguity is implicit in much social theory. Yet, over time, as theories become established, much of their openness to tension and ambiguity tends to be closed off. This article seeks to recapture some of that messiness, to shift the focus of attention slightly and to look at what slips out, does not fit or gets lost in translation. Drawing on the examples of two international organizations – the IMF and the World Bank – I explore the ways in which bureaucracies seek not only to contain ambiguity through various forms of quantification and standardization, but also to foster it.