This dissertation explores changes in and the influence of functional expertise on boards, specifically boards of health care organizations. In the first chapter, I explore how the composition of functional expertise changes following the onset of a crisis. Prior work has demonstrated that crises lead to heightened board member turnover. In this chapter, I confirm that crises lead to individual member turnover, and extend this research by showing how crises also lead to shifts in the composition of functional expertise. I find that crises lead to shifts in functional expertise that align with the crisis. I further show how a board's openness to change as influenced by board entrenchment, crisis severity, and environmental political ideology create variation in this relationship. In the second chapter, I explore how the composition of functional expertise relates to the fulfillment of different board responsibilities. I find that while the composition is not related to the fulfillment of most responsibilities, it does influence influence the degree to which boards fulfill their oversight function. Specifically, I find that complementarity between board expertise and the organization enhances oversight. Finally, in the the third chapter, I explore how the composition of functional expertise relates to board attention, with particular focus to the role of topically-aligned committees. I find that the composition of functional expertise is related to the time allotted to different board topics, that the likelihood of specific forms of expertise is related to have specialized committees with that expertise, and that these committees moderate the relationship between functional expertise and attention. Taken together, the findings in this dissertation theoretically contribute to understanding the evolution of functional expertise, replicating and extending upper echelons theory. Practically, the findings contribute to research on governance and health care management.