The absence of a correlation between age-adjusted death rates and the average income levels of economically developed countries has led researchers to conclude that income does not affect the mortality levels of economically developed countries. The mortality experiences of the former Soviet Union and some of the eastern European countries have further brought into question the importance of income's distribution in determining mortality among economically developed countries; prior to its breakup, the income distribution of the Soviet Union was as equal as that of Sweden, yet the life expectancy of the Soviets has been dramatically shorter than that of the Swedes. Using insights from a longitudinal microanalysis of U.S. mortality, this study presents evidence that, even for economically developed countries, the income distribution of a nation is an important determinant of its mortality. The results of this study also suggest that the relatively unequal income distribution of the United States is an important contributing factor to its low life expectancy relative to other high-income countries.