To establish a distribution of baseline sensitivity of Botrytis cinerea to pyrrolnitrin, an antibiotic produced by several biological control agents, 166 isolates collected from different crops were tested for sensitivity to pyrrolnitrin using a spore germination assay. Baseline EC50 (effective concentration to reduce spore germination by 50% comparing to the control) was determined. The results showed that the isolates exhibited a wide range of sensitivity to pyrrolnitrin, with a 8.4-fold difference in EC50 values between the least and the most sensitive isolates (from 0.0038 µg.ml-1 to 0.032 µg.ml-1). For all the isolates tested, the conidial germination was completely inhibited by pyrrolnitrin at doses above 0.1µg/ml. The efficacy of the pyrrolnitrin-producing Pseudomonas chlororaphis PhZ24 strain was tested in vitro on Petri plates and on tomato plants with isolates of B. cinerea having different EC50 values. Whatever the EC50 value of the isolates tested, no significant differences in sensitivity were observed towards this bacterium suggesting an absence of resistance to this biological control agent within B. cinerea isolates