The increase in income inequality in the United States over the past 20 years has been accompanied by a pronounced increase in economic segregation in urban areas. No research to date has analyzed the potential effects of such spatial segregation on mortality. To investigate these effects, the mortality experience of respondents aged 30 years and older on the 1986-94 National Health Interview Surveys residing in any one of 30 large metropolitan areas in the United States was analyzed. Concentrated poverty was associated with significantly elevated risk of mortality, even after controlling for individual household income. Concentrated affluence showed a consistent, protective effect only among the elderly. The effects were most pronounced among the poor, but were not confined to them. Urban planning should take into account the effects associated with economic residential segregation.