Although Missouri has had a Career Ladder program for teachers since 1987, there has been little research examining the program’s effects. This working paper, presented at a National Center on Performance Incentives conference, examines effects on student achievement, using longitudinal data on district math and reading scores for 524 Missouri school districts over a nine-year period. The paper compares achievement levels in participating districts with those of a matched group of nonparticipating districts. The estimated effects range from small positive effects to no effect. The authors conclude that, if the Career Ladder has a positive effect on test scores, it is probably very small. A soon-to-be-completed companion paper will explore program operations, and another will examine the relationship between Career Ladder participation and teacher retention.