The activity of alcohol acetyltransferase (AATase; EC 2.3.1.84) and esterase (EC 3.1.1.1) in two Saccharomyces cerevisiae strains during biological aging of a young wine was evaluated. The resulting wine was analysed for ethanol, isoamyl alcohols, ethyl acetate and isoamyl acetate. The products found at the end of the aging process (particularly for isoamyl alcohols and ethyl acetate) are correlated with the "flor" him thicknesses and enzyme activities tested. The contents of all these compounds decreased during aging, even in the control wines. Flor yeasts accelerated the disappearance of ethanol and ethyl acetate but delayed that of isoamyl alcohols and isoamyl acetate, particularly in the wines aged using race capensis, the aroma of which was thus enhanced.