A time course for laccase and cellulase genes transcription of Agaricus bisporus compost culture are examined. The results of assays for laccase gene leel show that the expression of this gene increased in the compost until pinning stage of development. In the fruiting cultures the amount of leel declined rapidly over a 4-5 d period immediately. Cellulase gene celS expression contrasted sharply appeared with leel expression by remaining at a low level until after the pins were seen. The cel3 concentration then increased some 10-fold. The cel3 expression remained high for some time and then declined during the later fruiting cycle. Gene expression for laccase and cellulase therefore correlates directly to the measurable level of extracellular enzyme activity and to biosynthesis of enzyme protein.