Breast-milk is arguably the ultimate functional food providing the nursing infant with basic nutrition as well as a complex mixture of immunomodulatory components, bioactive compounds and a vast array of hormones1. Having been breast-fed as an infant has been associated with enhanced cognitive development2 and may also provide protection against cardiovascular disease3,4, obesity5 and type 16 and type 2 diabetes7 later in life. Appropriate trace element intake is essential for optimal growth and development and as such may play a role in some of the positive outcomes associated with breastfeeding. Breast-fed infants are entirely dependent upon the mother to provide an appropriate trace element supply and evidence indicates that trace element requirements of term infants are generally met by exclusive breast-feeding through about the first 6 months of life8. After 6 months of age, introduction of complementary foods with adequate trace element content is essential to meet the nutritional needs of the growing infant. This is due in part to milk iron (Fe), zinc (Zn) and copper (Cu) concentrations declining throughout lactation9. Furthermore, milk Fe, Zn and Cu concentrations are relatively refractory to maternal trace mineral status10, even when the maternal diet varies considerably11. There is currently little information regarding the mechanisms through which the mammary gland regulates milk trace element concentrations. Similarities between humans and rodents12 allow us to use rodent models to examine the regulation of mammary gland mineral transport. Recently, several transporters for Fe, Zn and Cu have been found to control trace element uptake and efflux in various cell types. We have utilised the lactating rat to determine changes in mammary gland Fe, Cu and Zn transporter expression and localisation that occur throughout lactation and in response to maternal trace mineral deficiency in hopes of elucidating some of the changes which may be occurring in lactating women.