In order to know the background of Ki-ras gene mutations in the Chinese colorectal cancer,we first studied 35 colorectal cancer tissues using the PCR-RFLP method.Eleven of the 35 samples(31.4%) were found to contain Ki-ras codon 12 mutation,1 sample(2.9%) codon 61 mutation and there was no codon 13 Asp mutation frequently observed in the colorectal carcinoma of western countries.We also studied the mutations in the DNA of stcols from patients with colorectal cancer.We found Ki-ras cedon 12 mutation in 6 of 18(33.3%) stcol DNA samples.The same kind of mutatiOn was also observed in the corresponding tumor tissues.No Ki-ras gene mutation was found in normal stcols. Our data suggest that the established non-radioactive technique for detection of Ki-ras gene mutations in stool samples might be a usefully practical method for colorectal cancer screening at an early stage.