The HCT-8/5-FU multidrug-resistant colorectal cancer cell line has been successfully developed and because it has cross-resistance to 5-FU, ADM and DDP, it might serve as an ideal multidrug resistance (MDR) model for colorectal cancer research. The mechanism of HCT-8/5-FU resistance to chemotherapeutic agents might be related to the overexpression of P-170. Low concentrations of AG alone have no significant inhibition on HCT-8/5-FU and fail to induce apoptosis and to change cell cycles. AG might act as a chemosensitizer when co-administered with 5-FU, ADM and DDP, and the mechanism of reversal modulation of multidrug resistance by AG in the HCT-8/5-FU resistant cell line might be related to its downregulation of overexpression of P-170.