The introduction of recombinant DNA technology in the field of mushroom research has resulted in the cloning and characterization of a large number of genes. In order to study the genetics of compost colonization of A. bisporus, genes encoding enzymes involved in utilization of this substrate have been isolated. In addition, a number of genes which are induced in fruit bodies during fruit body development have been cloned and they will provide more insight in the genetics of this economically important aspect of the life cycle. Other genes that were cloned encode proteins of basic biochemical routes. They provide knowledge on the importance and regulation of these routes in the life cycle of A. bisporus and add to knowledge on the general architecture of A. bisporus genes. Here we present an overview of the currently available biochemical and molecular data of A. bisporus and we discuss the importance of the available genes as genetic markers for breeding purposes.