Introductory undergraduate courses play an outsized role in steering women and students of color out of STEM majors. One recent study, reported in Talking about Leaving Revisited, found that 35% of all decisions to switch out of a STEM major could be attributed to these courses, with women leaving at significantly higher rates than men. What is less well understood, however, is what it is about these courses that cause such differential responses across race and gender. This grant funds a team led by Anne-Barrie Hunter at the University of Colorado, Boulder, to conduct a large ethnographic study of introductory STEM courses across six U.S. college campuses. Focusing on courses in mathematics, computer science, chemistry, and biology with high DFWI (grades D, F, withdrawal, or incomplete) rates, the research team will conduct 240 in-depth, semi-structured interviews with professors, administrators, instructional staff, and teaching assistants and then link the information collected with university data on student performance. Interviews will be structured to examine the role that individual—as well as departmental and institutional—incentives, beliefs, attitudes, and practices have on student outcomes with an emphasis on teaching practices. The ethnography promises to yield important, actionable insights into the mechanisms that lead to differential racial and gendered outcomes among STEM students.