Strains of Hanseniaspora osmophila and Kloeckera corticis, isolated from wines produced by spontaneous fermentations of normal and dried grapes, were characterized for their fermentation behavior with and without SO(2) at 25 degrees C. All isolates behaved as glucophilic yeasts and yielded ethanol at concentrations of about 9% (v/v); acetic acid, acetaldehyde, ethyl acetate and acetoin were always produced to high concentrations. SO(2) addition had no significant effect on growth yield and fermentation rate. These metabolic features were maintained in the presence of 400 g l(-1) of sugars and at 15 degrees C, and were quite similar to those shown by Saccharomycodes ludwigii. Therefore, H. osmophila and K. corticis should be considered detrimental yeast species, particularly in fermentations of musts from dried grapes.