In this paper, discussion is restricted to indicators of educational system performance. By "educational system" is meant that system that is formally established within a country for the purpose of providing education according to the UNESCO definition of the term. What is said generally applies to indicators in other fields of the social sciences as well as to social and/or development indicators in general. The paper begins by establishing a theoretical model within which educational indicators can be defined and by discussing certain conceptual problems concerning the purposes for which indicators might be used and the methodological problems encountered in forming indicators. After a review of educational indicators developed to date, the paper develops a core of ten education indicators and demonstrates two approaches to using them to map educational systems performance across and within nations. The paper concludes by outlining research that may be conducted to extend both the core to indicators and the methodology proposed. (Author/IRT)