If current trends continue, international students will comprise half of U.S. science, technology, engineering, and mathematics (STEM) PhD graduates by 2020. The proportion of international PhD-level students on temporary visas to study STEM subjects in the United States has doubled over the past thirty years. Further, these students are much more likely than domestic students to major in and graduate with STEM-related doctoral degrees and to pursue careers in high-tech firms. The United States stands to lose its significant investment in these highly qualified students--and their potential contributions to U.S. entrepreneurship and innovation--if they return to their home countries after completing their degrees or post-doctoral work. The authors explore why foreign graduate students choose to study in the United States and what compels them to either remain in the country or return home after earning their degrees. They also compare their future plans with those of domestic graduate students. An appendix and the student survey are included.