['To study the effect of allicin on human colon cancer cell line LoVo and the combined effect of allicin and CPT-11 on this cancer cell line.', 'The LoVo cells were cultured in vitro and treated with allicin in different concentrations. MTT assay was used to test dynamically the cell growth inhibiting effect. Apoptosis induction (Annexin-V-FITC/PI) and modulation of DNA cell cycle were measured by flow cytometry. The change of cytotoxicity of CPT-11 after combination of allicin at the concentration of 4.0, 8.0 mg x L(-1) were investigated.', 'Allicin had inhibitive effect on growth of LoVo cells in a dose and time dependent manner, with IC50 value of 32.23, 10.74, 6.58 mg x L(-1) at 24 h, 48 h and 72 h, respectively. The apoptosis rate of LoVo cells increased progressively as the cells were treated with increasing concentration of allicin in 24 h, while the apoptosis rate achieved peak value when the cells were treated with allicin at the concentration of 8 mg x L(-1) in 48 h. The result indicated the low concentrations of allicin (< 4 mg x L(-1)) lead to G2/M cell cycle arrest, and higer concentrations ( > 4 mg x L(-1)) exert G1 + G2/M cell cycle arrest in 24 h. Compared with single use of CPT-11, the combined use of CPT-11 and allicin (4.0, 8.0 mg x L(-1), respectively) showed increasing cytotoxicity on the LoVo cells, with IC50 of 24 h decreasing from 47.5 to 7.4 and 7.2 mg x L(-1), respectively.'] Does [ Allicin enhance cytotoxicity of CPT-11 to colon cancer LoVo cell in vitro ]?