Even though the problem of grade repetition is high on the policy agenda of virtually every developing country, extremely little is known about either the causes or the educational effects of repetition. The general concern about grade repetition derives from the budgetary and social implications of having large numbers of repeaters taking up scarce positions in schools. This concern notwithstanding, fundamental disagreements about the nature of the problem have clearly inhibited the development of sensible policies. This research, replying on unique panel data for students in northeast Brazil, considers how the schooling system and individual students interact in determining enrollment patterns in primary schools. This investigation into underlying student and school behavior lays the groundwork for analysis of alternative policies. [reprinted in Nancy Birdsall and Richard H. Sabot (ed.), Opportunity Foregone: Education in Brazil(Washington, DC: Inter-American Development Bank, 1996), pp. 425-460.]