We look at some of the theoretical and methodological issues underlying international university ranking systems and, in particular, their conceptual connection with the idea of excellence. We then turn to a critical examination of the two best-known international university ranking systems--the "Times Higher Education Supplement (THES)" World University Rankings and the Shanghai Jiao Tong Academic Ranking of World Universities. We assess the various criteria used by the two systems and argue that the Jiao Tong system, although far from perfect, is a better indicator of university excellence. Based on our assessments of these two systems, we suggest how an ideal international university ranking system might look, concluding with some comments on the uses of ranking systems. (Contains 12 notes.)