This paper discusses the conceptual and methodological challenges facing two researchers investigating the development of interdisciplinary curricula in two new secondary schools, one in the UK and one in New Zealand. It is a discussion of research in progress that will be of interest to readers because of both the methodological challenges discussed and the research area itself. The key issue we identify is one for both researchers and teachers: how might the concepts and perspective of one discipline be brought into a relationship with another to enable deep learning? This question in turn highlights a key methodological challenge: developing the means to describe and evaluate new forms of curricular design and implementation where a traditional discipline-based curriculum has been rejected in favour of interdisciplinary ones. The integrative aims of interdisciplinarity are also examined. We employ Bernstein's (2000) concept of "knowledge structures" and "languages of description" to theorise a continuum of approaches to curriculum integration, from "functional" to "principled." This methodological manoeuvre is made possible by the development of a "translation device." This procedural mechanism makes accessible to analysis the organising principles that are in play in the interdisciplinary curriculum design practices we have observed. We conclude with recommendations for the interdisciplinary curriculum researcher.