This article examines equity in national systems of education in terms of differences in student outcomes, as measured by mathematics achievement scores on Programme for International Student Assessment (PISA) 2003. The author uses four measures for assessing equity in student outcomes: (1) the strength of the relationship between student socioeconomic status (SES) and math achievement; (2) the amount of variation in student achievement explained by differences between schools; (3) the size of the gap between high- and low-achieving students (also known as the "achievement tail"); and (4) the percentage of students who perform at low levels. Taken together, these four equity measures comprise the "dependent variable." This article includes two groups of variables that may be able to explain why some countries have more equitable student outcomes than others: (1) demographic and social variables; and (2) variables related to systems and structures of education. The demographic and social factors are measures about the level of poverty, income inequality, and immigration within the society. The educational variables are the type of secondary school structure and degree of privatization, selectivity, and school choice within the educational system. All of these variables have been found or suggested to have an influence on equity of student outcomes. The main approach taken in this article is to create a typology of equity in national educational systems in a sample of countries that participated in PISA 2003. Twelve countries were selected to provide a range of educational systems, levels of educational equity and demographic contexts. The equity measures for each country, along with a range of educational and social policies that characterize each educational system and its larger social context, are compiled into a table to allow patterns to be seen. A second table ranks the countries from most to least equitable along each equity measure. Finally, all four equity measure rankings are averaged to create an overall equity rank and score. The aim of the analysis is to: (1) show which countries are more equitable than others and along which equity dimensions; and (2) include a range of predictor variables to facilitate understanding about why some countries are more equitable than others. (Contains 2 tables and 1 note.)