International wage differences are important at a time of globalisation; their social and economic consequences are vast, if not devastating. It is astonishing, therefore, that the origins, causes, and determinants of international wage differences are hardly ever discussed. According to a widely held half-truth, international wage differences reflect international productivity differences. This study challenges that belief and shows that international wage differences are due to a mixture of discrimination and various economic factors, just like wage differences between the sexes. The approach of this study is influenced by two strands of socio-economic analysis, namely, by world-system analysis and by the feminist. critique of gender wage differences. The central theme is discrimination versus productivity. Are international wage differences due to productivity differences or are they due to discrimination? The following issues are examined: Data on international wage differences; long-term changes of national wage rates; wage differences due to gender, race, ethnicity, culture, and region; the relationship between wages and GDP per capita; and more.