Abstract: Objective To explore the relationship between organochlorine pesticides exposure and the incidence of breast cancer.Methods A case-control study was conduted with 98 cases and 79 controls.Fasting blood sample (5 mL) and breast adipose tissue specimens(10 g) were collected from every subject.The organochlorine residue level in the serum and fat were measured with gas chromatgraphy.Results There were significant differences in the residence between the cases and the controls(χ²=4.70,P< 0.05).For urban and rural patients,serum beta-hexachlorocye hexane (β-HCH) and pentachlorothioanisole(PCTA) levels were significantly different between cases and controls(P<0.05).Fat β-HCH,PCTA and dichlore-diphenyl dichloroethern(PP'-DDE) levels were significantly different between cases and controls(P< 0.05).Serum and fat β-HCH and PCTA levels were significantly different between cases and controls for estrogen receptor positive breast cancer patients(P< 0.05).Conclusion There may be a relationship between organochlorine pesticides exposure and the incidence of breast cancer,expecially for estrogen receptor positive breast cancer patients.