Childbearing among unmarried women has been the subject of intense public policy and public health concern for decades, much of it reflecting concerns about the impact on family structure and the economic security of children. Nonmarital births are at higher risk of having adverse birth outcomes such as low birthweight, preterm birth, and infant mortality than are children born to married women. Children born to single mothers typically have more limited social and financial resources. This report examines data on nonmarital births from the National Vital Statistics System (NVSS). The principal measures reviewed are the number of births to unmarried women, the birth rate for unmarried women, and the percentage of all births to unmarried women. The most recent data available are from the 2007 preliminary birth file. Data for 2006 are shown where the 2007 data are not available. Comparisons are also made with selected earlier years reflecting key points of change.