The number of students a mentor trains correlates with the protégés' future success, says a report in Nature this week (Nature 465, 622–626; 2010). Researchers at Northwestern University in Evanston, Illinois, used mentorship data from the Mathematics Genealogy Project to follow students. Metrics such as number of publications improved with the number of protégés mentored, but large pools of students later in a mentor's career led to protégés who themselves had 31% fewer protégés than expected. The authors suggest that mentors, later in their careers, might allot fewer resources to protégés; or students with low mentorship aspirations might court prolific mentors later in those mentors' careers.