Breast magnetic resonance imaging (MRI) screening has been shown to detect early breast cancer. The main challenge ahead for breast MRI screening is to prove its effectiveness in reducing breast cancer mortality. While this challenge is commonly viewed as a scientific, technological, and clinical one, it also carries ethical components. This article is concerned with the risks and benefits of MRI screening that should be explained to screening participants and discusses the evidence needed by policy makers who ultimately will determine a just allocation of health care resources to MRI breast cancer screening.