A phylogenetic analysis of more than 350 multicopper oxidases (MCOs) from fungi, insects, plants, and bacteria provided the basis for a refined classification of this enzyme family into laccases sensu stricto (basidiomycetous and ascomycetous), insect laccases, fungal pigment MCOs, fungal ferroxidases, ascorbate oxidases, plant laccase-like MCOs, and bilirubin oxidases. Within the largest group of enzymes, formed by the 125 basidiomycetous laccases, the gene phylogeny does not strictly follow the species phylogeny. The enzymes seem to group at least partially according to the lifestyle of the corresponding species. Analyses of the completely sequenced fungal genomes showed that the composition of MCOs in the different species can be very variable. Some species seem to encode only ferroxidases, whereas others have proteins which are distributed over up to four different functional clusters in the phylogenetic tree.