The first charter school law was passed in Minnesota in 1991 and with it, a new school reform movement began. After two decades, 41 states and Washington D.C. have adopted charter legislation. This special issue provides an opportunity for scholars to reflect upon the promises and limitations of charter schools and to offer policy advice for those in a position to influence future reforms. Together, the papers within this special issue examine the achievement effects of charter schools, their cost effectiveness, the competitive pressure created by charter schools, the degree to which charter schools are innovative and how some of the operational and policy features of charter schools may affect outcomes.