Twenty five isolates of Sclerotinia sclerotiorum were recovered from different infested fields of vegetable along the heavily cultivated crops in Jordan valley. Cellulase and pectinase activities of those isolates were detected using CMC and pectin agar media, respectively. Diameter of the clearing zones on those media represented the level of such enzymatic activities, characteristic of each isolate. The virulence of those isolates was studied using a squash (Cucurbita pipo) cultivar under a greenhouse condition. The significance of correlating the enzymatic activity with the virulence of the isolates was ascertained and discussed.