Objectives. To investigate the genetic susceptibility for breast cancer of Chinese

a hospital-based case-control study

pedigree survey and molecular genetic study were conducted. Methods. Logistic regression model and stratification methods were used in the risk factors analysis. Li-Mantel-Gart and Falconer methods were used to analyze the segregation ratio and heritability. Polymerase chain reaction（PCR） and polyacrylamide gel electrophoresis were used to detect AI

G-banding technique was used to detect the chromosome aberration of peripheral blood lymphocyte. Results. Family history of breast cancer is related to enhanced breast cancer risk significantly

OR is 3905（95%CI=1079～1413）

and it widely interacts with other risk factors. Accumulative incidence of breast cancer in first degree relatives is 999%

which is larger than that in second

third degree and non-blood relatives. Segregation ratio is 0021

heritability among first degree relatives is 356±58%. Frequencies of LOH at BRCA1 and BRCA2 loci in sporadic breast cancer are 612% and 577% respectively. In the sibs

both of them show LOH at D13S173 locus

and high frequencies of chromosome aberrations were observed. Conclusions. Genetic susceptibility contributes to breast cancer occurrence of Chinese

and its racial variation may be one of the important reasons for the large difference of incidence between western and eastern countries.