This chapter summarizes historical and modern approaches to fungal taxonomy, the current taxonomic standing of medically important fungi, and the implications for fungal nomenclature following the recent Amsterdam Declaration on Fungal Nomenclature, which prohibits dual nomenclature. Fungi comprise an entire kingdom, containing an estimated 1–10 million species. Traditionally, fungal identification was based on examination of morphological and phenotypic features, including the type of sexual spores they form and method of formation, and structural features of their asexual spores. Thus, many fungi have been described and named independently several times, based on either their sexual or asexual stages, resulting in a single genetic entity having multiple names. Recent molecular approaches to fungal identification have led to profound changes in fungal nomenclature and taxonomy. Certain phyla have now been disbanded, cryptic species have been identified via molecular approaches, and long-recognized species have been transferred to new genera, based on genotypic comparisons.
