Recent reports have demonstrated that the United States has a dropout crisis of alarming proportions. In some large-city school systems, more than 50% of students leave high school without a diploma. A large proportion of these dropouts have not accumulated enough credits to be promoted beyond ninth grade. Using survey and student record data for a cohort of Philadelphia public school students, the authors find that ninth-grade academic outcomes are not simply proxies for student characteristics measured during the pre-high school years and that ninth-grade outcomes add substantially to the ability to predict dropout. An implication is that efforts to decrease the dropout rate would do well to focus on the critical high school transition year. (Contains 3 tables.)