This is a report on the discussions (and post-re ections) of the MADIF10 symposium ”Conceptualizing a local instructional theory in design research”. Linking the discus- sion to Koeno Gravemeijer’s keynote at MADIF9 and drawing on di erent ongoing research projects, the aim of the symposium was to discuss [examples of] the opera- tionalization of design principles in order to deepen the understanding of some theo- retical concepts in design research. The contribution of the symposium is the inter- pretation of how local instruction theory interrelates with other concepts in design research, for instance, the hypothetical learning trajectory. The role of the concepts as both design tools and as outcomes was presented and discussed.