This study considered two questions about the use of national and state assessment databases: (1) Do state and national assessments provide the same information on the performance of an educational system? and (2) What are the factors that might affect the discrepancies between national and state assessment results? Kentucky and Maine were chosen for a case study. Four categories in the assessments of these states were compared with the same four categories of the National Assessment of Educational Progress (NAEP). While there were close similarities between the corresponding categories, it was risky to make direct comparisons without understanding how the NAEP and state assessments defined performance standards and how each state arrived at its own proficiency category labels. The percentage of students performing at or above high proficiency levels in the Maine and Kentucky assessments were not substantially different from the national assessment results. However, results were not entirely consistent across grades and years, a finding attributed to the fact that the definitions of performance standards and the methods of standard setting were different. The sizes of achievement gains from the state's own computations were greater than counterpart gains from the NAEP, something attributed to the high-stakes nature of the state assessments. These findings suggest that policymakers and educators need to become more aware of the uses and limitations of current national and state assessments as education information databases. (Contains 2 figures, 13 tables, and 12 references.) (SLD)