In this article, the authors present a study of experienced faculty's beliefs about the assessment of interdisciplinary student work. The study focuses on faculty's close analysis of student work produced in interdisciplinary courses, such as integrative final papers, written examinations, and capstone presentations. The authors begin by reviewing relevant literature on assessment and interdisciplinary learning in higher education and proceed with a description of the study and introduce their framework for targeted assessment. Building on their analysis of interviews and student work and in conjunction with the epistemic principles described in the paper, the authors highlight three core dimensions of students' interdisciplinary work: (1) disciplinary grounding; (2) advancement through integration; and (3) critical awareness. These three dimensions organize the presentation of faculty views of quality interdisciplinary work and the assessment challenges that they encountered. The results shed light on the qualities the faculty associated with more and less accomplished interdisciplinary student work and on the particular assessment challenges posed by work at disciplinary crossroads. Building on an educational research tradition that favors the development of "usable knowledge" (Lageman, 2002), the findings are integrated into a framework designed to focus evaluators' attention on the key qualities of interdisciplinary work worth attending to in assessment. In conclusion, the authors revisit the challenges and possibilities of more rigorous assessment and pedagogical support of interdisciplinary work. (Contains 1 figure and 4 notes.)