Fostering agency as a core component of professionalism is seen as a critical task of higher education. However, the tools for assessing university students' agency, and the pedagogical and relational resources needed for its development, are lacking. The present study describes the theoretical foundations and factor structure of the newly developed Agency of University Students (AUS) Scale, which assesses students' course-specific agency. In the factor analysis, 10 factors emerged. Four of these--Interest and motivation, Self-efficacy, Competence beliefs and Participation activity--are seen to represent individual resources of agency. The other four factors--Equal treatment, Teacher support, Peer support and Trust--represent relational sources of agency. Finally, Opportunities to influence and Opportunities to make choices represent contextual sources of agency. The psychometric properties and uses of the scale are discussed.