The number of systemically active antifungal agents has increased dramatically in recent years in response to the challenge of invasive mycoses. Additional work is needed to better understand the mechanisms of action of these agents as well as the mechanisms of resistance expressed by the fungal pathogens. Antifungal susceptibility testing has been standardized and refined and now may be considered to play an important role in the management of invasive mycoses. More work is needed to optimize the methods for testing new antifungal agents and for testing pathogens other than Candida. The ongoing efforts and international collaborations designed to address these issues will provide important information that will improve the management of serious fungal infections.