Policymakers and practitioners need new ways to understand patterns of neighborhood diversity (racial, ethnic, and economic) in their communities, and to track changes over time. This paper documents the prevalence of diverse neighborhoods, describes their geographic distribution, and explores how they changed between 1990 and 2000. It uses decennial census data to develop a new set of neighborhood typologies--grouping tracts into categories that reflect important differences in the racial, ethnic, and income groups represented. These typologies provide updated tools for describing the extent of neighborhood diversity and exploring the implications of diversity for families and communities.