Antibacterial, free radical scavenging, proliferative, and cytotoxicity effects of Doenjang extracts were examined. All samples except water extract showed strong antibacterial activity against oral bacteria, Streptococcus. pyogenes, S. mutants, S. sanguinis, S. sorbrinus, S. criceti, S. antinosus, S. gordonii, and Porphyromonas. gingivalis (MIC and MBC values: 0.08-1.25 and 0.16-2.50 mg/ml, respectively). DPPH method showed ethanol and ethyl acetate extracts are effective inhibitors of oral bacteria. Based on MTT assay, 24 h exposure to 0.31 mg/ml of all extracts, excepted water extract, resulted in strong cytotoxicity on KB cells. All extracts strongly inhibited human gingival fibroblast viability.