Projections by the President's Council of Advisors on Science and Technology (2012) point to a need for approximately one million more Science Technology Engineering and Mathematics (STEM) professionals than the U.S. will be able to produce considering the current rate of STEM postsecondary degree completions (Executive Office of the President of the United States, 2012). Do Advanced Placement® (AP®) courses in STEM complement the desire for more students completing STEM majors? In this study the authors ask if participation and performance in Advanced Placement STEM Exams in high school is predictive of a student's performance in STEM courses in the first year of college and the likelihood that a student will graduate with a STEM major, particularly for traditionally underrepresented populations in STEM fields--first-generation, underrepresented minority, and female students. The authors find that AP STEM examinees had 7% higher first-year STEM grades and a 13% higher probability of STEM major completion than matched non-AP STEM peers. Nearly all of these positive results held for first-generation, underrepresented minority, and female students.