The evaluation of educational programs has accelerated dramatically in the past quarter century. While such evaluations were once almost exclusively conducted in the U.S., they have broadened dramatically across many countries of the world. At the same time, the methodology has improved, strengthening considerably the internal validity of various studies. We must now consider what conclusions can be drawn from the growing wealth of international results. In particular, available cross-national studies on a variety of topics suggest using caution when generalizing results, because the results vary systematically with a number of institutional characteristics of the different countries that are not explicitly considered in within-country analyses.