The infant mortality rate, the number of deaths in the first year of life per 1,000 live births, is a widely used indicator of population health and well-being. In 2006, the overall infant mortality rate for the United States was 6.68, but infant mortality rates differed dramatically across racial and ethnic groups. Of every 1,000 live births, there were about five deaths among babies born to non-Hispanic white mothers and about 12 deaths among babies born to black mothers. The rate for babies born to Hispanic mothers was slightly lower than that for non-Hispanic white mothers. In this study, we use five years of micro-level data from 2000 through 2004 for non-Hispanic whites, blacks, Mexicans, Puerto Ricans, Asians, and Native Americans. We examine how infant mortality is associated with several background characteristics, including maternal marital status, education, and age. Using Census Bureau data on new mothers, we also look at the association between these characteristics and income and poverty. Our results provide new insights on the role of socioeconomic differences in infant mortality rates across racial and ethnic groups.