The International Association for the Evaluation of Educational Achievement has conducted a number of cross-national studies in which Western European countries participated. Results from the Second International Mathematics Study regarding the content and outcomes of this study in some Western European countries, Japan and the U.S.A. are presented and compared. The results show that comprehensive systems do not differ systematically from non-comprehensive systems with respect to achievement measures of students. However, measures of the implemented curriculum show differences which are consistent with system characteristics. Consequences for the comparative methodology are discussed.