OBJECTIVES: 1. Examine the impact of insurance on treatment of localized breast cancer using Breast Conserving Surgery (BCS) with radiation.  2. Identify factors that contribute to women’s receiving breast conserving surgery with radiation. METHODS: Breast cancer cases diagnosed during 1997-2002 were obtained from the Florida Cancer Data System.  Women aged 40 and above with localized breast cancer were included. Demographic, insurance, and treatment information were extracted and linked with 2000 Census data to get tract-level information on education and poverty level.  Multi-level logistic regression analysis was conducted to determine factors that have contributed to BCS with radiation treatment. RESULTS: 41,508 women were diagnosed with localized breast cancer in Florida during 1997-2002. The study found that BCS without radiation and mastectomy were the two major treatments for localized breast cancer.  The average age of the women was 66 years with 8.5% of them receiving BCS with radiation. Women with the following characteristics were more likely to receive BCS with radiation than their counterparts: having private or Medicare insurance, being married, living in neighborhood with higher percentage of high school education, and being recently diagnosed.  CONCLUSIONS: Although BCS with radiation is recommended to treat women with localized breast cancer by clinical practice guidelines and the use of this treatment has significantly increased over time, there are still differences in receiving the treatment among women with different health insurance and marital status. Possible reasons for the differences require further research.