The Génolevures website (http://cbi.labri.fr/Genolevures/ or http://genolevures.org/) provides tools and data relative to complete, partial, and mitochondrial genome sequences from 31 species of hemiascomycetes yeasts to facilitate comparative genomics studies of this clade. These sequences are manually annotated and regularly updated by a network of practicing experimental biologists from the Génolevures Consortium. Moreover, the Génolevures website has the benefit of continuous progress thanks to the constant addition of new annotated genomes, novel studies and new tools. The tools and data on the Génolevures website are organised around the typical questions of molecular evolution asked by biologists, such as the degree of gene conservation, the identification of species-specific, clade-specific or class-specific genes, the distribution of genes among functional families, and mechanisms of chromosome shuffling (cf.figure 1). Figure 1: The Génolevurs website : its tools and data (October 2009) All data from the Génolevures website are freely available, and instructions for proper citation are included in each section. The Génolevures website is developed using a ‘representational state transfer' architecture and URLs for individual identified resources built from the database can be constructed systematically.