In many developing countries, transmission of the human immunodeficiency virus (HIV) from mother to infant occurs through breast-feeding. Mastitis, an inflammatory process in the breast, may be common in lactating women in Africa and is associated with both higher HIV load in breast milk and mother-to-child transmission of HIV. Antioxidant micronutrient deficiencies may increase the risk of mastitis. Whether prevention, early diagnosis, and prompt treatment of mastitis will help reduce mother-to-child transmission of HIV in breast-feeding women needs further study.