Objective To investigate the microsatellite instability(MSI) and loss of heterozygosity(LOH) of BRCA1 gene at locus D17S855 in sporadic liver cancer in chinese,and their influence on the expression of corresponding genes of liver cancer,in order to provide laboratory basis for clinical treatment and prognosis analysis of liver cancer.Methods The following techniques were used in the study: extraction of DNA from paraffin-embedded tissues,polymerase chain reaction-single strand conformation polymorphism(PCR-SSCP),ordinary silver stain,Envision immunohistochemistry and Leica-Qwin computer imaging techniques.MSI and LOH of BRCA1 gene at locus D17S855 were detected and BRCA1 proteins were identified.Results MSI at locus D17S855 was positive in 14 of 74 samples of liver cancer(18.9%).MSI positive rate in TNM I+II(31.6%) was much higher than that in TNM III+IV(5.6%,P