The influence of four fermentative yeast strains, belonging to the Saccharomyces cerevisiae species, on the content of cis- and trans-resveratrol and resveratrol glucoside isomers in Vitis vinifera L. cv. Shiraz grape musts during alcoholic fermentation was studied by reverse phase high performance liquid chromatographic (RP-HPLC) analysis. During vinification, an increase in both the free and the glucosidic forms was observed up to day three/five (cis resveratrol/piceid) or day four (trans- isomers), after which variable yeast Â-glucosidase activity was noted until dryness, where a general increase in free forms of resveratrol was accompanied by a decrease in the corresponding glucoside. In the finished wines ready for bottling or aging, the total amount of all resveratrol forms reflected (P < 0.05) the manufacturers polyphenol extraction ratings for the strains. Relative extraction of total phenolics in red wine amongst different yeast strains was demonstrated to mimic relative stilbene content.