This chapter presents a selection of main theoretical and methodological coordinates and issues regarding descriptive translation studies (DTS) and polysystem theory (PT). It focuses on key authors and texts and on central concepts such as assumed translation, equivalence, untranslatability, translation norms and laws, (poly)systems, centre and periphery of a system, repertoire, and canonization; it also addresses ontological and epistemological considerations informing methodological choices. It ends with a consideration of critical topics and issues regarding DTS and PT.