Although Missouri has had a career ladder program for teachers since 1987, there has been little research examining the program's effects. This paper examines the program's effect on student achievement using longitudinal data on district math and reading scores for 524 Missouri school districts over a nine-year period. Our primary specification compares achievement levels in participating districts with a matched group of non-participating districts. We also examine alternative specifications, including controlling for prior district scores and using variation in district participation over time to look at within-district effects. Across the range of specifications, the estimated effects range from small positive effects to no effect in both subjects. We conclude that if the Career Ladder has a positive impact on test scores, it is probably very small. [This research brief describes work published by the National Center on Performance Incentives in "Missouri's Teacher Career Ladder Program" by Kevin Booker and Steven Glazerman, Working Paper 2008-15.]