In the presence of lycopene, we found a time-dependent influence on the MDA-MB-235 cell line, with an important decrease of the G2/M phase that reached 18%, which was explained by accumulation of cells in the G0/G1phase. MCF-7 cells exhibited the same changes but with no differences between time of exposure (48 and 96 h) (Table I). The MDA-MB-231 cell line underwent the major changes in cell viability when treated with lycopene and showed an important change in the percentages of cells in different cellcycle phases. After 96 h, a significant increase in the order of 10% of cells was observed in G0/G1phase with a decrease in the percentage of cells on S phase. No effect was observed after 48 h of treatment in MDA-MB-231 and MDA-MB-235 cell lines (Table I).