Accurate interpretations of large-scale assessment results and sound judgments about students' mathematical literacy depend on these assessments' validity and reliability. One important type of evidence towards this validation is the dimensionality analysis, which explores the conformity between the intended factorial structure (related closely to defining a construct--e.g., mathematical literacy, and its perception) and the statistical structure of the test results. This study investigates the dimensionality of mathematical literacy in PISA. Our results show that the structural relationship between PISA's theoretical (cognitive) and score interpretation frameworks is not at an expected level. These results have important implications for the way mathematical literacy is assessed from mathematics education and psychometric perspectives. [For the complete proceedings, see ED597799.]