In a two-year (2000 and 2001) investigation carried out in melon fields of Southern Italy, the antagonistic activity of the yeasts Rhodotorula glutinis, Cryptococcus laurentii and Aureobasidium pullulans against powdery mildew of cucurbits (Sphaerotheca fusca, sin. S. fuliginea) was evaluated. In both years, the antagonists reduced disease incidence on leaves significantly showing an activity comparable to that of the fungicide penconazole. In the first year the yeasts resulted more effective than biofungicide AQ10, while in the second year their activity resulted similar to that of AQ10. The antagonists showed a good survival on leaves surface even if the climate was quite hot and dry with rare rainfalls. Further investigations are necessary in order to optimise the activity of the new proposed biological means for the control of cucurbits powdery mildew.