The National Assessment of Educational Progress (NAEP) is a survey of American students' knowledge and skills in different subjects at grades 4, 8, and 12. NAEP combines the samples of performances to provide information about the knowledge and skills of students in the nation as a whole, in each participating state, and in different demographic groupings. The purpose of this report is to increase understanding of the achievement levels for the NAEP: what they are, and what they are not. The report is a reference for the American public, especially educators, parents, students, and policymakers. Seven booklets make up the report; each booklet focuses on one of the subjects for which NAEP achievement levels have been set. These include mathematics, science, reading, writing, civics, U.S. history, and geography. The information in this report will be helpful in interpreting accurately the meaning of the "Mathematics" NAEP achievement levels and student performance relative to the levels. The information will also aid in understanding the NAEP reports, commonly known as "The Nation's Report Card." Contents for this report include: (1) Understanding Achievement Levels for the Mathematics National Assessment of Educational Progress; (2) Overview of the Framework for the National Assessment of Educational Progress in Mathematics; (3) Achievement Levels: Descriptions and Cutscores; (4) Achievement Levels: Sample Items; and (5) Performance Data. (Contains 28 exhibits and 1 figure.)