Abstract: The effects of enzymatic-digested Se-enriched broccoli extracts (SeB) and selenocompounds on growth and antioxidative status in human colon cancer cells was investigated in this study. HCT116 and HCT116+Chr.3 cells were treated with selenocompounds (sodium selenite, sodium selenate, Se-Met, MeSeCys) or SeB [high-Se (H-SeB) or low-Se (L-SeB)]. The cytotoxicity induced by selenocompounds in HCT116 cells was not associated with cellular H2O2 level, while the differential cytotoxicity observed by sodium selenite between HCT116 and HCT116+Chr.3 cell lines was related to cellular H2O2 production with the change in antioxidative enzyme activity, and the restoration of chromosome 3. H-SeB was found to reduce the cellular H2O2 content in HCT116+Chr.3 cells. The results in this study indicate that regardless of Se content, the cytotoxicity in HCT116 cells of both SeB forms appeared to be H2O2-independent, whereas the cytotoxicity in HCT116+Chr.3 of either SeB form appeared to be H2O2-dependent with an increase in antioxidative ability for H-SeB.