This paper examines the gender gap in the likelihood that academic scientists join corporate scientific advisory boards (SABs). We assess (i) demand-side theories that relate the gap in scientists' rate of joining SABs to the opportunity structure of SAB invitations, and (ii) supply-side explanations that attribute the gap to scientists' preferences for work of this type. We statistically examine the demand- and supply-side perspectives in a national sample of 6,000 life scientists whose careers span more than 30 years. Holding constant professional achievement, network ties, employer characteristics and research foci, male scientists are almost twice as likely as females to serve on the SABs of biotechnology companies. We do not find evidence in our data supporting a choice-based explanation for the gender gap. Instead, demand-side theoretical perspectives focusing on gender-stereotyped perceptions and the unequal opportunities embedded in social networks appear to explain some of the gender gap.