Twenty-one US states currently offer some form of merit-based postsecondary financial aid, although the generosity and eligibility requirements of merit aid programs varies from state to state. This article uses nationally representative data from high school students in the early 1990s and the early 2000s to evaluate the relationship between the design of merit aid programs and their effects on student achievement and college trajectories. The findings suggest that programs that guarantee full tuition to recipients have greater effects on students' high school course-taking and college choice than less generous programs. Further, I find provisional evidence to suggest that programs with relatively simple merit-based eligibility requirements are more effective than programs with more complex means-tested eligibility requirements.