(-)-Epigallocatechin-3-gallate (EGCG), (-)-epigallocatechin (EGC), (-)-epicatechin-3-gallate (ECG), and (-)-epicatechin (EC) were found to have different cytotoxicities to human colon carcinoma LoVo cells. EGCG and EGC suppressed the growth of LoVo cells in dose-dependent manner; ECG and EC, however, had no obvious effects. At lower concentrations, EC did seem to promote slight proliferation. Similarly, EGCG and EGC, rather than ECG and EC, were found to induce apoptosis in LoVo cells. Moreover, EGCG, EGC, and ECG arrested G(1) phase in the cell cycle progression, whereas EC resulted in S phase arrest. We suggest that there are differences in the cytotoxicities of the four catechins to LoVo cells. They exert the effects by inducing apoptosis and regulating the cell cycle.