In yeast, the SNF1 gene product is essential for the release of catabolic repression. We report the isolation and characterization of an SNF1 homologue from the necrotrophic pathogen Sclerotinia sclerotiorum. Ss snf1 encodes a 765-amino-acid protein in which the catalytic domain has an overall identity with the yeast proteins varying from 55 to 76% while the C-terminal half of Ss SNF1 has a weak homology of about 20% with the yeast sequences. Reverse transcription-polymerase chain reaction showed that its transcripts were weakly and constitutively expressed in planta and in vitro regardless of the nature of the carbon sources and of the presence or absence of glucose. Expression of Ss snf1 in yeast cells allowed the snf1 mutant cells to utilize sucrose, raffinose or glycerol for growth while expression of the Ss snf1 catalytic domain did not restore growth on raffinose or glycerol. Ss SNF1 is structurally homologous to Snf1p, suggesting that the interactions between the kinase and the accessory subunits to activate the enzymatic complex are conserved in fungi.