Interest groups—collective voluntary organizations for which political advocacy is a primary task such as business associations and citizen groups—are key agents engaging with the bureaucracy. While understudied, research on the relations between interest groups and civil servants highlights the importance of the bureaucratic arena. Recent studies present different perspectives on the interactions between these two actors and also highlight the process of issue prioritization, an important aspect of (internal) agenda setting within groups. This is a key process to study as it provides insight into why groups allocate their attention and resources to a specific set of policy issues, and in this way it clarifies how interest groups put representation into practice. Issue prioritization within groups can be conceptualized as being guided by five drivers: internal responsiveness, policy capacities, niche seeking, political opportunity structure, and issue salience. Recent scholarship has highlighted how rather than privileging one driver over another, this process is first and foremost a balancing exercise in which groups take on board various internal and external considerations. Similar processes are at work within bureaucracies. The intersection of prioritization processes of civil servants and interest groups is an important area for future research.