Epistemic dependence and cooperative activity play important roles in much interdisciplinary research. In a recent analysis of epistemic dependence in interdisciplinary collaborations, Andersen & Wagenknecht have analyzed interdisciplinary research groups in terms of multilateral epistemic dependence between scientists engaged in a shared, cooperative activity. In this presentation, I shall build on this analysis, and by looking through the lenses of epistemic dependence and shared, cooperative activity I shall throw new light on some key issues in the discussions of interdisciplinarity, especially the notions of trading zones and of interactional and contributory expertise. The distinction between contributory and interactional expertise has been introduced as an distinction between, on the one hand, the expertise needed in order to contribute to the science of a given field (contributory expertise), and, on the other hand, the expertise needed in order to interact interestingly with participant of a given field (interactional expertise). However, this distinction was originally introduced based on sociologists’ fieldwork experience of learning the language of the scientists they studied while retaining their own material form of life and distinct contributory expertise. In this talk I shall argue that this differs in important ways from the situation of the collaborating scientists who produce joint contributions within an interdisciplinary area and that the main differences can adequately be expressed as differences with respect to whether they engage in a shared cooperative activity that includes epistemic dependence. On this basis, I shall propose a more detailed categorization of expertise in relation to interdisciplinary research.