This report is designed to help policymakers, parents, reporters, and foundation officials better understand what has been learned about voucher programs and why some key questions remain unsettled. It is based on an analysis of voucher programs in Milwaukee, Cleveland, and Florida State. Four basic questions are addressed: (1) What do we know from current studies of publicly funded voucher programs? (2) What more could we learn with additional research on these programs? (3) What key questions cannot be answered because of how existing program are structured? and (4) What can policymakers, researchers, and funders of research do to expand knowledge of vouchers? Key findings show that there is inconclusive evidence on the effectiveness of vouchers for improving education, that studies on vouchers have varying findings about student achievement, that voucher examples from other countries have not been fully examined, and that some questions will be difficult to answer no matter which research method is used. Recommendations include up-front evaluation requirements when authorizing a voucher program, performing long-term high-quality evaluation, and performing multiple kinds of studies. The report concludes with 19 references and an appendix containing major research questions that should be addressed by evaluations of any voucher program. (RT)