While college faculty are experts in their disciplines, teaching expertise is less understood. This paper explores one aspect of the pedagogical content knowledge of faculty new to teaching, specifically, knowledge of student difficulties. The project, conducted at three different institutions, used a case method, employing interviews and observations. Novices (N=11) were interviewed about the common difficulties students encountered in a specified introductory college course. Synthesis of data from the cases resulted in a working model of new faculty members' knowledge of student difficulties, including how difficulties are discerned, the actual content and processes of student difficulties, principles of action for overcoming difficulties, what faculty do in response to student difficulties, and how faculty know what they know about student difficulties. Results suggest that the core of what faculty know about student difficulties is represented by problems with specific content, problems with academic processes, and variables that affect students' understanding. Implications for faculty development and agendas for future research on this and other aspects of pedagogical content knowledge are included. (Contains 22 references.) (LL)