International scientific collaboration has increased both in volume and importance. In this article, the authors study the interpretation of macro-level data on international co authorship collaboration. They address such questions as how one might explain country- to-country differences in the rates of international coauthorship, networks of interna tional scientific collaboration among countries, and patterns of international collaboration in scientific fields. Attention is drawn to cognitive, social, historical, geopolitical, and economic factors as potential determinants of the observed patterns. They present a (...) methodology that gives one a measure, independent of size, of countries'propensities to collaborate internationally. (shrink)