Professional events that feature face-to-face interaction of social scientists from across the world are, next to publications and research, important forms of scientific knowledge production and dissemination. Thus, they are vital to the World Science System (WSS). Like other WSS elements, scholarly involvement in international social science events is characterized by unequal cross-national representation. This article focuses in-depth on the International Sociological Association (ISA), a major international social science professional association, to examine inequality in attendance at its flagship conferences. To what extent do countries differ with respect to the number of scholars attending ISA conferences? What factors drive attendance? The authors base their hypotheses on the economic, political and social dimensions that influence country representation. To test these hypotheses the authors use a dataset containing information on 212 countries and their participation in the eight ISA conferences – World Congresses and Forums – held from 1990 to 2012. Results show that a country’s GDP, level of democracy and social science research infrastructure (SSRI) substantially determine their level of representation. SSRI effects are significant above and beyond the effect of GDP and of other controls. Findings also show a meaningful over-time decrease in representation inequality according to countries’ GDP.