Sulfite is an antimicrobial agent used at the beginning of winemaking to avoid development of undesirable microorganisms. However, Oenococcus oeni, which is mainly responsible for the malolactic fermentation, has to grow in wine and therefore has to be resistant to sulfite. This study showed that acid-adapted cells of O. oeni survived better than non-adapted cells in the presence of a high sulfite concentration (30 mg l-1). Addition of a sub-lethal concentration of sulfite (15 mg l31) during the adaptation step in acidic medium increases the sulfite tolerance. Moreover, sulfite appeared to be able to induce a heat shocklike response. Our results suggest that pH homeostasis mechanisms and stress protein synthesis could be involved in the induction of sulfite tolerance in O. oeni.