The thesis of this chapter will be that cross-national studies of educational achievement have no more limitations than similar national or local studies, but that they do have more possibilities. The focus is on comparisons of achievement, but such studies lead us into curriculum and structure and methods and social class, and more. First, the history of comparative achievement studies will be reviewed, looking at the questions asked and the methods employed. A current example will be examined in some detail by way of arriving at tentative generalizations about both possibilities and limitations.