The cytotoxicity of extracts from Dolsan leaf mustard Kimchi (DLMK) treated with lactic acid bacteria on A 549 human lung cancer cells and SNU-601 human gastric cancer cells were investigated. Leuconostoc mesenteroides, Leu. gelidum and Weissella kimchii previously isolated from properly ripened DLMK were inoculated to DLMK as a starter ($1;{ imes};10^8;CFU/mL$). The DLMK was then fractionated by various extracting solvents. The cytotoxicity of MeOH extracts from DLMK on A549 and SNU-601 cancer cells was found to occur in a dose-dependent manner. Although the cytotoxicity of the MeOH extracts was found to be approximately 20 to 30% at concentrations of $250;{mu}g/mL$ by MTT(3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H tetrazolium bromide) assay, cytotoxicity of chloroform soluble fraction of DLMK treated with W. kimchii showed about 80 to 90%. Consequently, the growth of cancer cells was inhibited significantly in medium containing DLMK extracts. In addition, significant morphological changes such as cell condensation, cell fragmentation, and alterations in the size and shape of the cells were observed in cells grown in medium that contained the DLMK extracts. Taken together, these results suggest that inhibition of the proliferation of cancer cells by apoptosis was induced by DLMK extracts.