Comparison is fundamental to all forms of educational research. Traditionally, the field of comparative education has had a cross-national focus, though there is no inherent reason why this must be the case and indeed many insights can be gained from cross-fertilisation with the approaches of researchers who make comparisons across different units of analysis within countries. The field of international education is allied to that of comparative education, though has different emphases. This chapter reviews some of the meanings and parameters of the twin fields, and remarks on ways in which they can contribute both to each other and to other domains of enquiry.