What motivations drive scientists in their research and keep them going when things get tough? What rewards do they look for? Do these motivations mean that scientists have a unique relationship with their work and understanding of the distinction between work and leisure? Enthusiasm for their research and a strong desire to investigate problems that interest them are key motivations for our interviewees. The freedom to explore individual interests and the relative autonomy available in at least some research environments, are also valued, as are the opportunities to interact with colleagues from different cultures and scientific traditions. For many scientists work is fun, even something they admit to doing when they are not strictly ‘at work’ and the idea of fixed working hours is not something that they subscribe to.Material rewards are rarely primary motivations, and some even see their decision to pursue a life in science as a rejection of a materialistic world view and a commitment to a different value system. Above all there is a sense that in reflecting on their careers many scientists feel themselves to have been fortunate to have spent their working lives in science.