Abstract: The expression of small heat shock (shs) genes in presence of sulphite, was monitored in MRS medium supplemented with 40, 60 and 80 mg L-1 of potassium metabisulphite (K2S2O5). In all the experiments performed, the concentration of measured free sulphite was about 33% of the supplemented sulphite and no significant differences were observed between the pH values monitored though the experiment. Although high concentrations of sulphite (80 mg L-1) reduce drastically the viability of L. plantarum, cells were able to tolerate sub-letal doses of sulphite (40 and 60 mg L-1). RT-PCR revealed that the expression of shs genes analysed was different in presence of sulphite and was dependent from sulphite concentration. For all the shs genes an increase of cDNAs level was already observed at 40 mg L-1 of K2S2O5. The expression of the hsp 18.5 and hsp 19.3 genes, compared with the cDNA control, remained unchanged or even decreased after the concentration of sulphite was increased at 60 or 80 mg L-1, respectively. In contrast, hsp 18.55 expression increased at 60 mg L-1. The transcripts of all the genes analysed decreased in MRS supplemented with 80 mg L-1 of K2S2O5. These results suggest that a heat shock response like is probably confined to only some concentrations of sulphite in Lactobacillus plantarum.