The Teacher Advancement Program (TAP) was developed in the late 1990s by the Milken Family Foundation as a schoolwide policy to improve schools by raising teacher quality. Under the TAP model, teachers can earn extra pay and responsibilities through promotion to Mentor or Master Teacher and can earn annual performance bonuses based on a combination of their value added to student achievement and observed performance in the classroom. This report provides evidence on the impacts of TAP during the first year of its implementation in Chicago Public Schools (CPS). Funded in part by a federal Teacher Incentive Fund grant, CPS began implementing its version of TAP (called "Chicago TAP") in 2007 with 10 schools and plans to continue adding 10 new TAP schools each year of the grant's four-year implementation period. The authors designed a randomized experiment to estimate the impacts of Chicago TAP. To understand the first year of implementation of Chicago TAP they assessed how teacher development and compensation practices in TAP schools differ from practices normally implemented in Chicago public schools. They found that teachers in TAP schools reported receiving significantly more mentoring support than teachers in similar non-TAP (control) schools. While the introduction of TAP led to reported changes inside the school, these changes did not produce measurable impacts on student test scores as of March of the first year of the program. They did find evidence that TAP increased school retention. Teachers in TAP schools did not report significantly higher satisfaction or more positive attitudes toward their principals than did control teachers. Supplemental Tables are appended. (Contains 8 footnotes, 4 figures, and 27 tables.)