Background: The prevalence of breast cancer is about one third of all cancers in women constitute the second most common cancer after lung cancer and the most common cause of cancer death among women. Because of high prevalence, study of effective factors on breast cancer in Ardabil area is a very important.

Method: In this case-control study, 100 women were selected from the breast cancer clinic that referred to hospitals in the Ardabil city in 2014 year. In addition, 100 healthy women were that referred to health centers in Ardabil city, selected for cluster and were considered as the control group. For statistical analysis and investigation of the influencing factors on breast cancer used to classification tree models.

Results: The analyses indicated that, 83 women from case group and 80 women from control group were married. The most common age for patients whit breast cancer was 15-49 years old with average 32/8 year and (SD= 8.3).40% of women whit breast cancer were less than 30 years. None of the women did not have breast secretions in the control groups but 43 women in case groups have breast secretions.

Conclusion: The identification of risk factors in this study can be programmed to prevent and control breast cancer.

Keywords: Cancer, Breast, Ardabil