The article provides an overview of the mathematics assessment program of the Organization for Economic Cooperation and Developments’ (OECD) Program for Student Assessment (PISA). As such, it provides a comparative view of the PISA results for Canada, Mexico, and the United States. It outlines the program, its frameworks, and competencies PISA uses to describe the achievement of 15-year-olds in over 40 countries participating in the PISA assessments. Particular attention is given to the PISA conception of mathematical literacy and cross-disciplinary problem-solving. These two areas were a focus of the 2003 assessment. In addition to a discussion of general results, two sample problems are presented, one from the mathematical literacy and one from cross-disciplinary problem-solving, along with detailed information about student performances in the items. The article concludes with a consideration of the lessons to be learned from the PISA study relative to the teaching and learning of mathematics.