In late January through early March of 2003, the National Assessment of Educational Progress (NAEP) grade 4 and 8 reading and mathematics assessments were administered to representative samples of students in approximately 100 public schools in each state. The results of these assessments were announced in November 2003. Each state also carried out its own reading and mathematics assessments in the 2002-2003 school year, most including grades 4 and 8. This report addresses the question of whether the results published by NAEP are comparable to the results published by individual state testing programs. Comparisons to address the following four questions are based purely on results of testing and do not compare the content of NAEP and state assessments. How do states' achievement standards compare with each other and with NAEP? Are NAEP and state assessment results correlated across schools? Do NAEP and state assessments agree on achievement trends over time? Do NAEP and state assessments agree on achievement gaps between subgroups? Although this report does not focus on Adequate Yearly Progress (AYP) measurement specifically, it does focus on the measurement of mathematics achievement, and specifically on comparisons of the messages conveyed by NAEP mathematics assessment results and state mathematics assessment results. These comparisons center on four facets of NAEP and state assessment results: (1) achievement standards; (2) school-level achievement percentages; (3) achievement trends; and (4) achievement gaps. These facets of comparisons are summarized in this volume. The following are appended: (1) Methodological Notes; (2) Tables of State Mathematics Standards and Tables of Standard Errors; and (3) Standard NAEP Estimates. (Contains 47 tables, 29 figures, and 6 footnotes.)