This chapter analyzes how one particular governance mechanism affects the performance of research teams. We look at an external requirement for interdisciplinarity and internationality of Research Training Groups (RTGs) and study how their performance is affected. We expect to observe two countervailing effects with changes in interdisciplinarity and/or internatio-nality: first, increased performance due to an increase in productive resources and a second, decreased performance due to increased team problems (communication, conflicts etc). Since both effects are expected to vary with the disciplinary field of research, we separate our analysis for the Humanities & Social Sciences in comparison to the Natural & Life Sciences and indeed find different effects in the different disciplinary fields. Furthermore, we separately analyze the effects of interdisciplinarity on the one hand and internationality on the other hand. We conclude that the effectiveness of a particular governance mechanism varies substantially between the disciplinary fields and for the type of heterogeneity under consideration. Therefore governance of research should be either precisely engineered to a particular disciplinary field and a given type of heterogeneity or it should offer a menu of options that allows research teams to choose from according to their specific needs.