This study was carried out to get a picture of risk factors associated with the occurrence of cancer breast. Three hundred and seventy two females (180 breast cancer patients and 192 controls) were selected from Ain Shams and Benha University Hospitals to be the subjects of this study. The results showed that the important risk factors affecting the development of cancer breast were : parity, age at first birth, age of menarche, age of the patient, family history, number of pregnancies and age of natural menopause. Mostly these factors are interrelated to each other.