I study how CEOs affect corporate behaviors and R&D workers. I use health-related CEO turnovers (e.g., deaths) for identification. My difference-in-differences design compares firms with CEO turnovers to firms without. I find that inventors leave firms suddenly after CEO turnovers, especially when CEOs without STEM degrees succeed CEOs with STEM degrees (STEM CEOs). Text analysis of 10K filings suggests that STEM CEOs emphasize innovation, which retains inventors. But event studies indicate that having STEM CEOs negatively affects firms' stock prices. Patent citation analysis suggests why: while STEM CEOs may retain valuable R&D workers, they may overlook less-innovative but valuable R&D projects.