This report presents findings from a retrospective study of the academic histories of International Baccalaureate (IB) students and other students in the state of Florida. The IB Diploma Program is an internationally recognized college-preparatory curriculum designed to provide students with a rigorous and comprehensive academic experience. IB has grown dramatically in recent years and is thought by many to be among the best college-preparatory programs in existence. As such, there is tremendous interest in the potential impacts of IB, but any attempts to examine those impacts must deal with selection bias that results from the voluntary participation of schools and students. Failure to do so makes it impossible to determine whether the performance of participating students was actually influenced by IB, or whether the outcomes for these students would have been just as good without IB. As a critical step in understanding the impacts of IB, the analyses presented in this report examined the selection mechanisms behind IB participation across Florida, the state with the second highest representation of IB programs in the nation. We use longitudinal student and school-level data from 1995 through 2009 from the Florida K-20 Education Data Warehouse (EDW) to characterize individual students’ educational histories from elementary school through high school and into college. To address issues of selection bias, we use propensity score methods (Rosenbaum & Rubin, 1983) to adjust for preexisting differences between IB and non-IB students.