Cell-wall protein profiles of different strains of Lactobacillus helveticus and L. delbrueckii subsp. lactis isolated from regional cheeses were studied by SDS-PAGE. The patterns were highly reproducible and the presence of numerous bands with molecular weight ranging from 14 to 160 kDa allowed L. delbrueckii subsp. lactis to be differentiated from L. helveticus. The method is a reliable and rapid way to identify thermophilic lactobacilli.