In this paper we explore the practice of interdisciplinarity by examining how the UK research councils addressed the problem of the sustainable city during the 1990s. In developing their research programmes, the councils recognised that the problems of the sustainable city transcended conventional disciplinary boundaries and that an interdisciplinary approach was needed. In practice, however, initially radical proposals to research the city as a complex combination of science and technology and society contracted into more cognate collaborations that emphasised either science or technology or society, with the result that interdisciplinarity came to be located within research councils rather than between them. This, in turn, led to the development of a third kind of interdisciplinarity as the responsibility for making the connections between the research programmes was outsourced to the user communities—the local authorities. Unfortunately, local authorities struggled to find the resources to conduct this work so that the radical interdisciplinarity recommended at the start of the decade remained unaccomplished at the end. In describing these events we emphasise roles of paradigms and epistemic cultures in shaping research approaches and the complications they raise for the triangulation between approaches that is assumed in the idea of interdisciplinarity. We do not wish to be entirely negative, however, and conclude by suggesting some ways in which the quality and success of this much-needed interdisciplinary work could be increased.