High-skilled immigrants are a very important component of U.S. innovation and entrepreneurship. Immigrants account for roughly a quarter of U.S. workers in these fields, and they have a similar contribution in terms of output measures like patents or firm starts. This contribution has been rapidly growing over the last three decades. In terms of quality, the average skilled immigrant appears to be better trained to work in these fields, but conditional on educational attainment of comparable quality to natives. The exception to this is that immigrants have a disproportionate impact among the very highest achievers (e.g., Nobel Prize winners). Studies regarding the impact of immigrants on natives tend to find limited consequences in the short-run, while the results in the long-run are more varied and much less certain. Immigrants in the United States aid business and technology exchanges with their home countries, but the overall effect that the migration has on the home country remains unclear. We know very little about return migration of workers engaged in innovation and entrepreneurship, except that it is rapidly growing in importance.