In collaboration with the Maternal and Child Hospital Research Center of Mongolia, a cross-sectional study of 400 pregnant women and their offspring is being conducted in rural and urban sites of the country. The study is assessing whether the in utero environment differs in women living a “traditional” lifestyle compared with those living a more urban lifestyle, and by degree of Western acculturation among those who have recently migrated to the capital city, UlaanBaatar. In addition, researchers are studying the endocrine profile of pre-menopausal women living in the capital by migration status among mothers of girls participating in a study of milk consumption and hormonal status presently being conducted at Harvard Medical School. A recent publication demonstrated that breast cancer incidence in Mongolia is almost a third of rates in China. Rates within Mongolia appear to have increased slightly over the last decade and are higher in urban than rural areas. The increase in breast cancer incidence with age plateaus at menopause, as in other Asian populations.