Pay for performance is not a new idea, and reformers should not ignore the dismal record of merit pay over the past century. Initially adopted with a flourish of expectations during several waves of popularity in the past, every plan eventually fell into disuse. These plans proved to be unexpectedly costly and cumbersome to run. They often generated cynicism and unproductive competition among teachers. Recent developments, though, may change the prospects of using pay to reward teachers' performance. Given these developments in methods and attitudes, people can ask whether today's pay reform plans will fare better than those of the past. To better understand the experiments under way, the authors reviewed programs from across the country that pay teachers for how well they teach and what their students achieve. They studied four school districts' programs in more detail--Houston, Minneapolis, Charlotte-Mecklenburg, North Carolina, and Hillsborough County, Florida. The study of four school districts uncovers the messy reality of adding merit bonuses to the salary scale. The four school districts' pay plans differ in how they assess teachers' performance and how they award the bonus money.