In an attempt to understand regional differences in the efficacy of biocontrol against Sclerotinia sclerotiorum in France, strains of the pathogen were collected from different locations and tested for their susceptibility to the biocontrol fungus Coniothyrium minitans. Based on results obtained for the first 22 strains examined, wide and highly significant differences were observed, suggesting that the efficacy of this biocontrol method could vary locally depending on the frequency of susceptible vs less susceptible strains of S. sclerotiorum. However, the differences in susceptibility observed so far for strains from the North and the South of France cannot explain global regional differences in the efficacy of this biocontrol method. If confirmed by ongoing work on additional strains of S. sclerotiorum, these results will point to other hypotheses examined in the framework of national project "ScleroLeg".