Policymakers in developing countries areincreasingly recognizing the necessity of developingstrategies and identifying specific investment programs toreduce spatial differences in living standards within theirnational territories. Choosing among alternate policyinstruments to support spatial convergence is notstraightforward. Should the focus be social policies thatsupport human development in lagging regions and promotemigration to leading regions? Or infrastructure policiesthat connect lagging regions with markets in leading ones?Or investment and regulatory policies to create new clustersof economic activity in regions not favored by the market?The 2009 World Development Report (WDR) provides a policyframework for integrating lagging and leading areas withincountries, prioritizing and sequencing policy instrumentsbased on the severity of the territorial integrationchallenge. To operationalize the WDR's policypriorities, this report discusses analytic tools to measurethe magnitude of regional disparities and identify where andin what activities specific policies and investments can bemost effective. It also highlights potential economic andsocial tradeoffs of alternative policy instruments forpursuing spatial equity. Country case studies are providedto illustrate how these tools either inform a specificpolicy debate on territorial development or have beendirectly used to guide ongoing policy discussions betweenthe Bank and counterparts in national and sub national governments.