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. We explore why foreign doctoral students choose to study in the United States and what compels them to either remain in the country or return home after earning their PhDs. We also compare their future plans with those of domestic PhD students.