The incidence rate of breast cancer in developed countries is almost three-fold higher than in developingcountries. Iran has had one of the lowest incidence rates for breast cancer in the world, but during the recentdecades a marked increase has been seen. The purpose of this study was to investigate some established riskfactors of breast cancer in Iranian women. A study of 11,850 women participating in abreast screening programwas conducted. The 197 women diagnosed with breast cancer and 11,653 healthy women were compared. Logisticregression was performed to investigate associations of reproductive and anthropometric factors with breastcancer risk. Family history of breast cancer (OR=1.94 , 95%CI=1.35-2.78), occupation (OR= 1.65,95%CI=1.20-2.25), education level (OR=0.50,95%CI=0.28-0.91), parity (OR=0.27, 95%CI=0.12-0.59), menopausal status(OR=3.15, 95%CI=2.35-4.21), age at menarche (OR=0.33, 95%CI=0.15-0.70), and age at the first pregnancy(OR=4.10 , 95%CI=1.13-14.77) were related to the risk of breast cancer. Decrease in parity may to some extentexplain the rising trend of incidence of breast cancer incidence in Iranian women.