The availability of new antifungal agents has multiplied the demand for in vitro antifungal susceptibility testing for Aspergillus spp. The European Committee on Antimicrobial Susceptibility Testing (EUCAST) has charged its Antifungal Susceptibility Testing Subcommittee (AFST-EUCAST) with the preparation of new guidelines for in vitro susceptibility testing of antifungals against Aspergillus spp (EUCAST-AST-ASPERGILLUS). This committee has modified the reference method for broth dilution antifungal susceptibility testing of filamentous fungi (M38-A) as follows: (i) RPMI 1640 supplemented with 2% glucose (RPMI 2%G) as assay medium, (ii) inoculum preparation by conidium counting in a haemocytometer and (iii) an inoculum size of 2x105-5x105 CFU/ml. The incubation time is about 48 h at 35 degrees C and MIC is read visually. The MIC value is a no-growth visual endpoint. The standard method described herein is intended to provide a valid and economic method for testing the susceptibility to antifungal agents of Aspergillus spp., to identify resistance, and to facilitate an acceptable degree of conformity, e.g. agreement within specified ranges and between laboratories in measuring the susceptibility.