Protection against fungal pathogens can theoretically be elicited by vaccines that stimulate humoral or cellular immunity, or both. There is conclusive evidence that humoral immunity can modify the course of infection against certain pathogenic fungi such as Candida albicans and Cryptococcus neoformans. However, for other fungi, such as Aspergillus fumigatus, the notion that humoral immunity contributes to host defence is unproven. Attempts to evaluate the potential efficacy of humoral immunity using immune sera are often inconclusive, whereas consistent results can be obtained with monoclonal antibodies. Protective monoclonal antibodies can be used to identify antigens that induce useful humoral responses.