The U.S. Department of Education released data from the Third International Mathematics and Science Study (TIMSS) to serve as a “starting point to examine U.S. education, student achievement, teaching and curricula.” The researchers and administrators of TIMSS hoped that these findings would provoke reflective discussions by providing a different lens through which schools could reevaluate their current practices and education policymakers could benefit from new insights. In the three years following the release of the first set of data, a number of states, districts, and schools have delved deeply into TIMSS for policy development and school improvement, receiving assistance through meaningful collaborations. U.S. researchers, practitioners, and policymakers have been working together with data from TIMSS and other research studies to generate viable solutions for improving student achievement in mathematics and science. This Policy Brief stems from one such effort—a TIMSS Policy Forum that was held in Washington, D.C. in 1999. At the Forum, researchers described the questions they were seeking to answer using TIMSS data, and practitioners and state and local policymakers described the tactics they were taking to support school improvement using those research findings. The interdependence among research, policy, and practice demonstrated at the Forum and reported in this Brief serves as a model for a national conversation on education that is grounded in both information and its practical application. The initiatives, outlined below, undertaken in the three districts, one school, and one state illustrate the impact that meaningful data and useful interpretations of those data can have on education policy and practice. By closely comparing and contrasting the curricula, teaching practices, professional development, and administration policies of many countries, researchers, policymakers, and practitioners can jointly assess what might work best for students in the United States.