Because we can identify almost every individual who has earned a Ph.D. from a U.S. university, we have knowledge of the population from which academic entrepreneurs in the life sciences hail. Moreover, using information recorded in scientific journal articles, it is possible to construct relatively detailed career histories for academic scientists. Therefore, wewere able to draw a probability sample of doctoral degree holders in the life sciences and track members’ work histories. We combine these data with information on university scientists who have ventured into commercial science to analyze rates of transition to the role of entrepreneur.