Pleurotus ostreatus showed atypical laccase production in submerged vs. solid-state fermentation. Cultures grown in submerged fermentation produced laccase at 13,000 U l(-1), with a biomass production of 5.6 g l(-1) and four laccase isoforms. However, cultures grown in solid-state fermentation had a much lower laccase activity of 2,430 U l(-1), biomass production of 4.5 g l(-1), and three laccase isoforms. These results show that P. ostreatus performs much better in submerged fermentation than in solid-state fermentation. This is the first report that shows such atypical behavior in the production of extracellular laccases by fungi.