The effects of different yeast starters and SO(2) addition on malolactic fermentation in a new winery were evaluated by a molecular approach in three vintages. Alcoholic fermentations with 40 and 100mgl(-1) SO(2) were carried out, followed by uninoculated malolactic fermentations. Isolated colonies of Oenococcus oeni obtained from samples throughout the vinification were identified and typified by multiplex RAPD-PCR. This made it possible to monitor the population dynamics and follow the proportion of as many as 29 different indigenous strains. In one of the vintages, O. oeni strains were more inhibited when a specific yeast starter was used.