Following the collapse of the Soviet Union, Bulgaria, along with other Central and Eastern European countries, began a transition towards a democratic political system and market-oriented economy. Socio-economic and political changes associated with this transition have created a growing need for a new kind of citizenry, one equipped with flexible and practically oriented knowledge and skills. In order to make progress towards this goal, the Bulgarian Ministry of Education and Science (MoES) has engaged in several reform initiatives, including the setting of standards that detail the content that students will study at each grade level within each subject area. These new standards set the expectation that students will gain proficiency in core subject areas and learn the same content regardless of socioeconomic background, ethnic origin, or geographical location. While equality of educational opportunity has long been a core principal of the Central and Eastern European socialist states, there has been limited research on either equality of access to educational opportunities or the level of equality in educational outcomes as these countries have moved towards participatory democracy and market economies. As decentralization of implementation has accompanied centralized curricular reform, understanding how both equality of opportunity and equality of outcomes vary within countries has taken on increasing importance. This article begins to fill this gap using data from the 2003 Trends in International Mathematics and Science Study (TIMSS) to document the level of variation in mathematics and science proficiency outcomes in Bulgaria and by examining the degree to which this variation is associated with the socio-economic background of students, the region where the students are enrolled, the type of school that they attend, as well as their degree of access to teachers with different levels of background and knowledge in mathematics and science, and differences in the use of inquiry-oriented instruction in their classes. (Contains 6 tables, 1 figure and 1 note.)