Antifungal pharmacokinetics and pharmacodynamics (PK–PD) has been used to develop currently available antifungal agents, and further optimize their use for critically ill patients. New experimental models have been developed to enable drug concentration–effect relationships to be characterized. This chapter describes the tools that have been developed and are available for antifungal PK–PD. The PK–PD of currently available antifungal drug classes and agents within those classes are reviewed. As knowledge improves, antifungal PK–PD will become a critical component for the development of new agents.