This dissertation studies the motives of scientists. The scientific reward system puts much emphasis on the non-financial rewards of science: intellectual challenge and independence (their taste for science). As such, economists have for a long time implicitly assumed that all scientists consider these factors important. This assumption does not stand up to empirical investigation: scientists differ in their motives. Many scientists care less about independence and intellectual challenge, but more about financial rewards such as money and career progress. They also make career decisions, such as the choice to work in industry or academe, in line with their motives. This thesis contributes to this topic by investigating how the motives of scientists relate to four unexplored aspects of scientists careers. More specifically, it studies international mobility decisions (chapter 1), wage differentials between industry and academe (chapter 2), the career choices of researchers in industry (chapter 3), and the exit of scientists out of academe (chapter 4). These topics are studied using Belgian data on Ph.D. scientists who responded to the Careers of Doctorate Holders survey.Chapter one proposes a novel perspective of international scientist mobility. Extant literature concludes that academic scientists need to go abroad early in their careers in order to build experience, networks, and credibility. This chapter argues that researchers with a stronger taste for science have stronger incentives to engage in international mobility. The results show that scientists with a higher taste for science are indeed significantly more likely to report international mobility than others. Moreover, researchers with a stronger taste for science tend to travel to countries with on average more highly ranked universities, and researchers with more general career-oriented motives tend go abroad for shorter periods of time. Chapter two considers the industry-academe wage gap. Even though it a stylized fact that researchers can earn more in industry than in academe, there is no economic research which explicitly examines this gap. We contribute to this by first estimating the wage gap while correcting for self-selection according to motives and differences in research focus. Second, the corrected wage gap is examined to explore how it differs among scientists with different motives and across scientists pursuing different kinds of research. The results show that the descriptive wage gap is overestimated by approximately twenty percent. Further, the wage gap faced by an academic scientist increases in time spent on development and decreases in time spend on research. These results thus show that not all academic scientists would earn more in industry. Chapter three investigates how scientists motives relate to job characteristics in industry. Do scientists with more science-related motives find science-intense positions in industry? The chapter analyses this in three dimensions: the scientific orientation of the firm, the research focus of the job,and whether the job entails linkage with the scientific community. The results show that only researchers who combine a high taste for science with a preference for monetary incentives and general work rewards are more likely to work in science-engaged firms than in others, to work in jobs with a strong research component, or to link to the scientific community. Depending on the level of analysis, fifty to sixty percent of researchers with a high taste for science do not work in science-intense firms or jobs. Chapter four assesses which researchers leave academe. The results confirm that scientific publications are one of the most important determinants of academic survival: the chance of leaving decreases with 6% per additional publication. Scientists who patent are much more likely to leave academe even though patenting scientists have above average publication records.