Producing sufficient numbers of graduates who are prepared for science, technology, engineering, and mathematics (STEM) occupations has become a national priority in the United States. To attain this goal, some policymakers have targeted reducing STEM attrition in college, arguing that retaining more students in STEM fields in college is a low-cost, fast way to produce the STEM professionals that the nation needs. The purpose of this book is to gain a better understanding of this attrition by determining rates of attrition from STEM and non-STEM fields; identifying characteristics of students who leave STEM fields; comparing the STEM course-taking and performance of STEM leavers and persisters; and examining the strength of various factors' associations with STEM attrition. This book is also intended to serve as a primer for outlining existing STEM education policy issues and programs. It includes assessments of the federal STEM education effort and the condition of STEM education in the United States, as well as an analysis of several of the policy issues central to the contemporary federal conversation about STEM education.