In this chapter we discuss social and ethical dimensions of breast screening. Breast screening has influenced, and been influenced by, attitudes toward the breast and breast cancer, increasing emphasis on responsibility and risk in healthcare, and prevailing in biomedical approaches to early detection of cancer, technological innovation, and evidence-based medicine. Commercial and advocacy interests, and the political nature of breast screening have shaped its social character. Ethical considerations in breast screening include maximizing benefit (within resource constraints), minimizing harm, delivering more benefits than harms, respecting autonomy, maintaining honesty, transparency and just decision-making, respecting privacy, distributing benefits and burdens fairly, and valuing reciprocity and solidarity. We discuss these, and consider ethical challenges including disputes over evidence of benefit and harm, and balancing conflicting ethical principles. Attending to social and ethical aspects of screening will assist policymakers and practitioners to proceed in a justifiable and legitimate way.