The Program for International Student Assessment (PISA) is a system of international assessments that measures 15-year-olds? capabilities in reading literacy, mathematics literacy, and science literacy every 3 years. PISA was first implemented in 2000 and is carried out by the Organization for Economic Cooperation and Development (OECD), an intergovernmental organization of industrialized countries. Each PISA data-collection effort assesses one subject area in depth, even as all three are assessed in each cycle so that participating countries have an ongoing source of achievement data in every subject area. In addition to the major subject areas of reading literacy, mathematics literacy, and science literacy, PISA also measures general or cross-curricular competencies such as learning strategies. In this second cycle, PISA 2003, mathematics literacy was the subject area assessed in depth, along with the new cross-curricular area of problem solving. Major findings for 2003 in mathematics literacy and problem solving are provided here, as well as brief discussions of student performance in reading literacy and science literacy and changes in performance between 2000 and 2003. The following are appended: (1) Technical Notes; (2) Reference Tables; (3) TIMSS-PISA 2003 Expert Panelists; and (4) PISA Online Resources and Publications. (Contains 12 figures and 27 tables.)