Cortbase is a nomenclatural database for corticioid (resupinate) fungi (Corticiaceae s.l. and related hymenomycetes) with basionyms, synonyms, taxonomically correct names, data on name usage, literature references, and evaluation of nomenclatural status. It is available as an on-line service (http://andromeda.botany.gu.se/cortbase.html) and as an MS-DOS executable for local installation. The database includes 8112 species names; of the 4412 basionyms included, 2101 represent taxonomically acceptable species, 1434 are heterotypic synonyms, and 877 are of uncertain application. The improvements over the previous version include the new, platform- independent on-line search interface, some 800 more corticioid names, numerous additions to the existing data, and six new categories for searching, including searches for location of type specimens and for authors of species names.