OBJECTIVE: To investigate the effect of lactic acid bacteria isolated from fermented mustard on immunopotentiating activity METHODS: One hundred and fifty nine strains of lactic acid bacteria isolated from traditional Taiwan fermented mustard were evaluated for their immunopotentiating activity on a murine macrophage cell line RAW 264.7. RESULTS: Of the strains, pronounced increases in the levels of nitric oxide (NO), tumor necrosis factor-α and interleukin-6 were observed in strains B0040, B0110 and B0145. Among them, strain B0145 had the highest NO and tumor necrosis factor-α generation in RAW 264.7 cells; strains B0040 and B0110 were also superior to that of Lactobacillus casei. These results demonstrated that NO and cytokines were effectively induced when the bacterial stimulants were treated with macrophages. In addition, strains B0040 and B0110 were identified as Lactobacillus plantarum, and B0145 as Weissella cibaria using 16S rDNA analysis. CONCLUSIONS: The results implicated selected strains may be regarded as a biological response modifier and had a broad application prospects in exploiting new functional food or as a feed additive.