With the rising incidence of fungal infections and a widening range of antifungal agents, determining the in vitro susceptibility of microfungi to antifungals is increasingly important. Recent years have seen standardization of methods suitable for testing the susceptibility of yeasts and filamentous fungi to antifungals and a wider choice of commercially supplied kits for determining susceptibility derived from those standards. The texts surveys standard microdilution quantitative methods, disk diffusion tests and assessment of commercially available tests suitable for routine use in mycology laboratories. The Etest is recommended for its high correlation with the CLSI standards and sophisticated methodology including interpretation, which guarantees high quality and reproducible results. To assess pharmacokinetics, determination of antifungal levels in the patient's serum is recommended.