Cladistic analyses were used to assess monophyly for genera of corticioid fungi (Hymenomycetes, Basidiomycota). Based on parsimony analysis, many genera were found to be paraphyletic; to recognize only monophyletic taxa, 50 genera have been synonymized and 142 presumably monophyletic genera retained for further analysis. Over 12 000 equally parsimonious trees are possible for the 142 taxa. Although consensus trees leave much of the phylogeny unresolved, more than 10 monophyletic groups can be distinguished based on 95% majority-rule consensus, including the families Atheliaceae, Botryobasidiaceae, Hericiaceae (syn.: Gloeocystidiellaceae), Peniophoraceae (syn.: Stereaceae), Schizophyllaceae (syn.: Meruliaceae) and Xenasmataceae. The use of representative species in cladistic analysis is not recommended. To avoid the use of paraphyletic genera (and unnecessary nomenclatural changes), robust taxonomic systems are needed which avoid unnecessary splitting. Key words: fungal taxonomy, Hymenomycetes, Corticiaceae, classification.