Current DNA extraction protocols for genomic DNA from Botrytis cinerea almost always start with mycelium that has been reduced to powder with liquid N(2) in a mortar, and this makes their application to a large number of samples slow and cumbersome. Here we present an adaptation of an existing method [Moller et al. (1992) Nucleic Acids Res 20: 6115-6116] for which the initial steps have been modified, including the homogenization of the fungus with sand and the aid of a common household drill. This method allows the processing of large number of samples in much shorter times and generates an average of 4 mu g DNA per sample, of sufficient quality for use in PCR and Southern blotting.