Clinical and Laboratory Standards Institute document M38-A2--Reference Method for Broth Dilution Antifungal Susceptibility Testing of Filamentous Fungi; Approved Standard--Second Edition describes a method for testing the susceptibility of filamentous fungi (moulds) that cause invasive (Aspergillus spp., Fusarium spp., Rhizopus oryzae (R. arrhizus), Pseudallescheria boydii [Scedosporium apiospermum], S. prolificans, Sporothrix schenckii, and other opportunistic pathogenic moulds) and cutaneous (dermatophyte, Trichophyton, Microsporum, and Epidermophyton spp.) fungal infections to antifungal agents. Selection of antifungal agents; preparation of antifungal stock solutions and dilutions for testing, implementation, and interpretation of test procedures; and the purpose and implementation of quality control procedures are discussed. A careful examination of the responsibilities of the manufacturer and the user in quality control is also presented.