Gatekeeper courses such as Anatomy and Physiology are often referenced in discussions regarding the national shortage of persons in allied health professions. In an attempt to bolster access to STEM professions, some community colleges are mandating prerequisite courses such as Natural Sciences and/or General Biology for STEM gatekeeping courses. In this study, we examined which of these prerequisite courses helped students to pass Anatomy and Physiology and whether the courses are an additional barrier to STEM field completion. This was the first study to evaluate whether a prerequisite course was predictive of success in Anatomy and Physiology, and it contributes to the body of literature regarding student success in the sciences.