Genetics provides an approach to the analysis of the complex function of lignin biodegradation, through the isolation of mutants and the creation of gene libraries for the identification of genes and their products. However, white-rot fungi (for example, Phanerochaete chrysosporium) have not so far been analysed from this point of view, and there is the challenge of establishing such genetics. P. chrysosporium is convenient experimentally because relatively few genes are switched on at the onset of ligninolytic activity. We describe the isolation of clones carrying genes expressed specifically in the ligninolytic phase, the development of a general strategy for mapping such clones, and the elucidation of the mating system of this organism. Another objective is the development of methods for transforming DNA into P. chrysosporium. This would allow the use of site-directed mutagenesis to analyse the functioning of ligninases, and the control of expression of the corresponding genes. The use of genetic crosses for strain improvement and the identification of components of the system are also discussed.