Background GDP per capita is arguably the single most predictive determinant of health at the nationallevel, yet such a measure fails to capture the complexity of wealth (and thus health) distribution within a population. Health at the individual level has been shown to be associated with asset-based measures of wealth, but the relationship hasn’t been demonstrated consistently at the national level. Currently existing wealth and inequality measures are not comparable across surveys, across countries, or across time. In this thesis, I quantify wealth inequality using an asset-based measure by country and year, from 1990 to 2010, and study associations between inequality and several measures of health through the lens of the Millennium Development Goals. Methods I generate a global asset-based wealth index that is comparable across countries and over time using 461 surveys from 140 countries, anchoring this scale on assets with low differential item functioning. I then translate this to an international dollar scale for the calculation of a modified Gini coefficient and ratio of 90th to 10th percentiles. I then investigate the relationship between such measures and child and maternal mortality in terms of levels, trends and thresholds of improvement in the Millennium Development Goal 4 & 5 targets after controlling for other known determinants of these health outcomes. Findings Wealth-based inequality is consistently significantly associated with maternal and child mortality at the country level, regardless of inequality metric selected. A counterfactual scenario reducing inequality in 1990 by one standard deviation suggests that countries would have lower mortality rates now, would have seen more rapid progress in reducing mortality from 1990 to 2010, and that more would be on track to achieve the Millennium Development Goal targets. Interpretation The observed associations between income inequality and health outcomes add new evidence to the debate around the possible detrimental effects of economic inequality. The findings here suggest that the reduction of economic inequality, through provision of services or redistributive policies, may be critical for improve health outcomes in the long run.