Data from numerous studies show that lumpectomy (breast-conserving therapy) plus radiation therapy provides survival equivalent to that following mastectomy (either modified radical or radical mastectomy) for patients with ductal carcinoma in situ (DCIS). According to the data from the National Cancer Data Base and the Surveillance Epidemiology End Results (SEER) Program, use of lumpectomy among female DCIS patients has increased dramatically over the last decade. This study examined population-based trends in treatment for DCIS among Louisiana women and compared the trends with the SEER data. Our data revealed that the percentage of the DCIS patients who received a lumpectomy increased from 34.3% in 1988-1991 to 53.7% in 1996-1999 in Louisiana (p<0.05) while DCIS patients who received a modified radical mastectomy decreased from 51.7% to 26.1% (p<0.05). Increasing use of lumpectomy was seen across all races, age groups, rural/urban areas, and poverty-level areas. Utilization of lumpectomy was about the same for white and African-American women but varied by age group, rural/urban area, and poverty level. Female DCIS patients residing in rural areas or high poverty level areas were less likely to receive a lumpectomy than those residing in urban or affluent areas. Among the patients who had a lumpectomy, 34.4% received post-lumpectomy radiotherapy in the first study period (1988-1991) and 49.7% in the last study period (1996-1999). In Louisiana, utilization of post-lumpectomy radiotherapy decreased with advancing age. Despite the increase in use of lumpectomy, its utilization remained approximately 10% lower than in the SEER areas throughout the study period. A similar deficit was observed for post-lumpectomy radiation therapy.