Education is widely perceived to be a tonic for the rising inequality that often accompanies development. But most developing-country governments tilt their education spending toward higher education, which disproportionately benefits elites. We find that in countries with high "tertiary tilts," rising primary enrollment is associated a decade later with far higher inequality-not the lower Gini coefficients many would expect. Since most developing countries tilt their spending toward higher education, our analysis suggests that efforts that concentrate only on expanding mass education, such as the UN's Millennium Campaign, could end up raising inequality in much of the developing world.We are grateful to