Background There has been an increase in the incidence of breast cancer in China,but no definite risk and protective factors for breast cancer have been identified in Chinese females.This study was designed to identify the risk factors for female breast cancer in North and East China.Methods A 1:3 matched,case-control study was conducted.All of the subjects in the case and control groups were selected from a previous epidemiological survey of 122 058 females aged 25 to 70 years.Single and multiple Logistic regression analyses were used to study potential factors in the development of breast cancer.Results Significant differences at the level of α=0.20 between case and control groups were observed for the following factors:economic status,social status,family annual income,bean product consumption,body mass index (BMI),family history of breast cancer in the first or second degree,number of miscarriages,menstrual pattern,benign breast disease history,nipple leakage,inverted nipple,history of diabetes mellitus,history of hypertension,history of ovarian cyst,physical exercise,current and global quality of life satisfaction,healthy behavior and prevention,and scores of breast cancer-related knowledge.After Cox-regression model analysis (α=0.10),six factors were found to be significantly related to breast cancer,of which the ORs and 95％C/s were:BMI,1.696 (1.169-2.460,P=0.005); benign breast disease history,2.672 (0.848-8.416,P=0.093); family history of breast cancer,7.080 (1.758-28.551,P=0.006); number of miscarriages,1.738 (1.014-2.978,P=0.044); global quality of life satisfaction,3.044 (1.804-5.136,P=0.000); healthy behavior and prevention,3.294 (1.692-6.412,P=0.000).Conclusions A comprehensive range of factors related to breast cancer was identified.Women should be educated about a healthy lifestyle,especially those with a family history of breast cancer or a personal history of benign breast disease.