We are developing a Masters programme to build on the success of our interdisciplinary undergraduate programme. By its nature, an MRes in Interdisciplinary Study must be broad, and cannot prescribe particular skills or knowledge. Moreover, what content do you build in when the students have a wide variety of disciplinary backgrounds and aspirations? Our innovative solution is the ‘Open Box’ module. This module will give students complete control over the content of their course, drawing from within the institution and the wealth of resources available externally. They will need to identify key gaps in their skills and knowledge required to undertake their interdisciplinary research project, and we need to provide the intellectual and progressive framework to support this activity in a dynamic way. With each student building their own bespoke module, key questions are: 1. How do you assess students when they are studying different subjects? 2. How do you ensure that the material they are choosing is appropriate and rigorous? 3. How do you account for the variation in levels that they may be studying at? In this presentation, we will outline some of the potential solutions to these questions, but welcome discussion and ideas from the audience.