Aims: During fermentation yeast cells should cope with stress conditions. We pursue a better understanding of the stress response in wine yeasts at the beginning of vinification. Methods and Results: We analyse by means of quantitative PCR the expression of several stress induced genes in 24 efficient commercial wine yeast strains at the beginning of vinifications performed under standard conditions or with small variations in pH and temperature. In all cases, high levels (with differences among strains) of GPD1 mRNA but quite low expression of other stress genes (TRX2, HSP104 and SSA3) were found. For all these genes, mRNA levels increase as temperature decreases or pH increases. Conclusions: Important levels of expression of GPD1 (but not of other stress genes) are required during the first hours of vinification, because of the need for glycerol production to counteract the hyperosmotic stress at this point. The differences among strains suggest that certain level of expression is enough to ensure the continuity of the process. Variations in the pH and temperature of the vinification can affect gene expression. Significance and Impact of the Study: A common pattern of stress response between efficient wine strains exists, which could be used as a criterion for selection. Studies of this kind can allow the establishment of connections between gene expression and physiological traits.