Although scholars have long studied circumstances that shape prejudice, inquiry into factors associated with long-term prejudice reduction has been more limited. Using a 6-year longitudinal study of non-Black physicians in training (N = 3,134), we examined the effect of three medical-school factors—interracial contact, medical-school environment, and diversity training—on explicit and implicit racial bias measured during medical residency. When accounting for all three factors, previous contact, and baseline bias, we found that quality of contact continued to predict lower explicit and implicit bias, although the effects were very small. Racial climate, modeling of bias, and hours of diversity training in medical school were not consistently related to less explicit or implicit bias during residency. These results highlight the benefits of interracial contact during an impactful experience such as medical school. Ultimately, professional institutions can play a role in reducing anti-Black bias by encouraging more frequent, and especially more favorable, interracial contact.