Objective To evaluate denaturing gradient gel electrophoresis (DGGE) in detection of single nucleotide polymorphisms or mutations of APEX gene in colorectal cancers.Method Five exons of APEX gene in colorectal cancers were screened by DGGE following sequencing.The relationship between the band mobility patterns of DGGE and results of DNA sequencing were studied and the related literatures were reviewed.Results According to the principles of DGGE as well as the experimental findings,it was observed that whatever the bases were changed,only one of four patterns of DNA bands presented on DGGE and three of these patterns were identified on denaturing gradient gels in this research.Heterozygotes were characterized by four bands at different levels on a lane of denatured gels and homozygotes just presented one band.Each band represented one type of DNA molecules.The DNA molecules with a mismatch were always got behind those molecules without mismatch on gels.When the base mutated from A/T to G/C,the mutant DNA molecules moved faster and was located in front of the wild-type molecules ongels.When the base mutated from G/C to A/T,the results of electrophoresis was contrary.Conclusions For a known SNP,the genotypes and allele frequencies can be determined by the patterns of DNA bands on denaturing gradient gels with exemption of sequencing,while for the mutant DGGE may be helpful to predict the changes of base mutations,which will be favorable to correctly analyze the results of sequencing.