This paper addresses the conceptual and practical difficulties in interdisciplinary cooperation between the natural sciences and the social sciences. The perspective taken is that of Rural Development Sociology of the Social Sciences group of Wageningen University and Research Center. It is proposed to use the term transdisciplinarity in order to better express the fact that the outcomes of integrated projects definitely move beyond any of the disciplines involved. But they can also be sub-optimal from a mono-sectoral or mono-disciplinary point of view. Coastal area development and watershed management are used as examples. In Wageningen, international education is directly related to transdisciplinary research, especially within the social sciences.