This article discusses major issues of interdisciplinary research. In the introduction, the concepts of ›disciplinarity‹, ›multidisciplinarity‹, ›interdisciplinarity‹ and ›transdisciplinarity‹ are being explicated. This is followed by a comparative treatment of experiences with designing and practicing interdisciplinarity in various fields of the humanities and social sciences. In a nutshell, the overall result of this is disappointing: far too often, the interdisciplinarity promised in grant proposals is little more than just rhetoric. The last part of the paper is devoted to an archaeological case study, that is, the Langobards project of the Römisch-Germanische Kommission at Frankfurt.