Students enter courses in engineering with intuitions about physical phenomena. Through coursework they build on their intuition to develop a set of beliefs about the subject. Often, their understanding of basic concepts is incomplete and their explanations are not "correct." Concept Inventories are assessment tools designed to determine the degree to which students understand the concepts of a subject and to identify the bases for misunderstandings. A cooperative effort between faculty at the Universities of Wisconsin and Illinois has been undertaken to develop a concept inventory for heat transfer. The process initiated with student identification of the conceptual problems rather than with faculty perceptions of student misunderstandings. Students then explored areas of conceptual difficulty and phrased questions that would test understanding of the concepts. Students working together with faculty developed a concept inventory for heat transfer. The presentation will report on the experience with using student groups and the resulting concept inventory.