Two novel Lactobacillus strains, C-5-1(T) and HB5, were isolated from the walls of a distilled spirit fermenting cellar in Hebei province, China. The strains were Gram-positive, non-spore-forming, non-motile curved rods and were facultatively anaerobic. They produced 5% (-)-D/95% (+)-L lactic acid exclusively from glucose fermentation, but were catalase-negative. Both strains fermented N-acetylglucosamine, arbutin, salicin, cellobiose, maltose, trehalose and beta-gentiobiose. The mean DNA G+C content of the two strains was 46.9+/-0.8 mol% (46.4 mol% for the type strain, C-5-1(T)). Phylogenetic analysis based on 16S rRNA gene sequence similarity showed that strain C-5-1(T) was clustered in the Lactobacillus casei/Pediococcus phylogenetic group and was closely related to Pediococcus dextrinicus JCM 5887(T) (97.9% similarity), followed by Lactobacillus algidus JCM 10491(T) (93.9% similarity). The DNA-DNA relatedness between the type strain C-5-1(T) and P. dextrinicus JCM 5887(T) and L. algidus JCM 10491(T) was only 5.4 and 4.3%, respectively. Therefore, based on phenotypic, genotypic and phylogenetic analyses, a novel Lactobacillus species, Lactobacillus concavus sp. nov., is proposed. The type strain is C-5-1(T) (=AS 1.5017(T)=LMG 22739(T)).