While in some higher education contexts a separation of teaching and summative assessment is assumed to be self-evident, in other contexts the opposite is regarded to be obvious. In this article the different arguments supporting either position are analyzed. Based on a systematic literature review, arguments for and against are classified at the micro-, meso- and macro-level. Articles specifically discuss the way in which making use of an external examiner influences the learning environment, the quality assurance policy and the policy of an institution with respect to the outside world (users, other institutions, etc.). In addition, the literature reveals that the suggested arguments and positions for and against disentangling instructional roles are highly context specific. Strikingly, empirical evidence for these arguments is rather scarce. There is a need, therefore, for a systematic research program which investigates the influence of the large and diverse set of assumptions and presuppositions on the disentangling of instructional roles. (Contains 1 table.)