The aim of this study was to determine the in vitro activity of propolis extract against 67 yeasts isolated from onychomycosis in patients attending at the Teaching and Research Laboratory of Clinical Analysis of the State University of Maringá. The method used was an adaptation made from the protocol approved by the National Committee for Clinical Laboratory Standards. The yeasts tested were: Candida parapsilosis 35%, C. tropicalis 23%, C. albicans 13%, and other species 29%. The propolis extract showed excellent performance regarding its antifungal activity: the concentration capable of inhibiting the all of the yeasts was 5 x 10(-2) mg/ml of flavonoids and 2 x 10(-2) mg/ml of flavonoids stimulated their cellular death. Trichosporon sp. were the most sensitive species, showing MIC50 and MIC90 of 1.25 x 10(-2) mg/ml of flavonoids, and C. tropicalis was the most resistant, with CFM50 of 5 x 10(-2) mg/ml of flavonoids and MFC90 of 10 x 10(-2) mg/ml. In view of the fact that propolis is a natural, low cost, nontoxic product with proven antifungal activity, it should be considered as another option in the onychomycosis treatment.