Better-educated people are healthier, although the sources of this relationship remain unclear. Starting with basic principles of consumer theory, we develop a model of how health disparities are determined that does not depend on the precise causal mechanism. Improvements in the productivity of health care disproportionately benefit the heaviest health care users. Since richer patients tend to use the most health care, this suggests that new technologiesby making more diseases treatable, reducing the price of health care, or improving health care productivitycould widen socioeconomic disparities in health. An exception to this rule, however, is a simplifying technology, which can contract health disparities, since richer patients are more likely to invest effort in adhering to complex treatment regimens. We present a few empirical case studies to help illustrate the theoretical results. First, we show that a complicated treatment regimen (antiretroviral therapy for HIV) benefited well-educated patients disproportionately. In contrast, simplifying drugs for hypertension coincided with a contraction in cardiovascular disparities not seen in other diseases. Finally, nationally representative data suggest that there are wider disparities by education among the chronically ill populationsprecisely the population one would expect to be the heaviest health care users.