The cytotoxic effects of partially purified substances from Bacillus polylfermenticus SCD toward a variety tumor cell lines were studied. Cytotoxic activity was determined with regard to the A549 (human lung carcinoma), AGS (human stomach adenocarcinoma), DLD-1 (human colon adenocarcinoma), HEC-1-B (human uterus adenocarcinoma), SW-156 (human kidney carcinoma), and NIH/3T3 (murine normal fibroblast) cell lines using the MTT assay. Cytotoxic substances were partially purified through Diaion HP-20 columns and extracted with methanol or other organic solvents (n-hexane, chloroform, ethylacetate, and butanol). B. polyfermenticus SCD supernatant showed up to 60% inhibition of cell viability fer all five human cancer cell lines tested. When treated with 10 mg/mL of n-hexane, chloroform, ethylacetate, and butanol extract, HEC-1-B cells showed a 25,62,35, and 63% rate of inhibition respectively, and AGS cells showed a 72, 61, 44, and 67% rate of inhibition, respectively. At a concentration of 10 mg/mL, 100% methanol Diaion HP-20 extracts showed inhibition rates of 97.0% toward A-549 cells, 98.1% toward AGS cells, 81.6% toward DLD-1 cells, 83.5% toward HEC-1-B cells, and 92.7% toward SW-156 cells. These results indicate that partially purified fractions from B. polyfermenticus SCD have the potential to inhibit not only colon cancer cells, but also lung, stomach uterus, and kidney cancer cells. Further studies are needed to characterize the cytotoxic substances released in B. polyfermenticus SCD cultures.