There is a well known large and persistent association between education and health. This relationship has been observed in many countries and time periods, and for a wide variety of health measures. The differences between the more and the less educated are significant: in 1999, the age-adjusted mortality rate of high school dropouts ages 25 to 64 was more than twice as large as the mortality rate of those with some college. Substantial attention has been paid to these "health inequalities." Gradients in health by education are now being systematically monitored in many countries (the United States includes them as part of its Healthy People 2010 goals), and countries such as the United Kingdom have target goals of reducing health disparities--specifically by education or factors correlated with education. In this paper, we review what is known and not known about the relationship between education and health, in particular about the possible causal relationships between education and health and the mechanisms behind them. We then assess the extent to which education policies can or should be thought of as health policies. Data Appendix is included. (Contains 3 tables, 3 figures and 13 endnotes.)