Denver Public Schools utilizes one of the nation's highest profile alternative teacher compensation systems, and a key element of Denver's Professional Compensation System for Teachers (ProComp) is pay for performance. This study analyzes the student achievement implications of ProComp utilizing matched student- and teacher-level data from 2003 to 2010. We find that student achievement increased during the years ProComp was implemented, but that these gains were observed for students taught by teachers enrolled in ProComp's alternative compensation system as well as non-participating teachers. While the findings are not consistent across grades and subjects, there is some evidence that teachers voluntarily opting into ProComp are more effective than those who do not volunteer. Finally, some ProComp bonuses were well targeted towards value-added measures of teacher effectiveness while others were not. (Contains 4 figures and 6 tables.)