Abstract： Objective To study the relationship between sensitivity to 5-FU and the status of a panel of microsatellite loci in three human colon cancer cell lines. Methods Cell viability in several concentrations of 5-FU was assessed by the MTT test. Expression of hMSH2 and hMLH1 in LoVo, SW480 and SW1116 cells were analyzed by immunocytochemical staining. Ten mononucleotide and dinucleotide microsatellite loci were analyzed by the PCR-SSLP-silver staining method. Results By MTT assay, it showed that LoVo cells were more sensitive than SW480 and SW1116 cells (0.8 μmol/L, 2.2 μmol/L and 1.9 μmol/L, respectively, P<0.05). By immunocytochemical staining, hMSH2 was expressed in SW480 and SW1116 cells but not in LoVo cells, while hMLH1 was positive in all three cell lines. The PCR-SSLP-silver staining of 10 microsatellite loci revealed that LoVo cells had a different pattern of electrophoretic bands compared with SW480 and SW1116 cells, manifesting both additions and band-shifts. Conclusion Together with hMSH2 and hMLH1, the status of a panel of microsatellite loci may be used as convenient predictors for drug-optimization or prognosis-assessment in colorectal cancer patients before chemotherapy.