Breast cancer represents a significant disease burden in Kentucky, affecting some 2,900 newly diagnosed women each year. About 600 Kentucky women will die of breast cancer in 2001. Kentucky's age-adjusted death rate for breast cancer in 1995 was 24.2 per 100,000 women, ranking 30th in the United States. In Kentucky and nationally, it is known that breast cancer treatment and prognosis may be complicated by elderly women's age and comorbid illnesses. Not all differences in treatment and prognosis can be explained, however, by patient characteristics or illness severity. A large body of health services research has developed over the last thirty years that documents the relationship between the supply of health care resources (e.g., physicians, hospital beds) and variances in treatment. This line of research has particular significance in Kentucky, where the supply of resources varies greatly across the state. Because breast cancer treatment variations unrelated to breast cancer disease may affect prognosis and outcome, it is important that these treatment variations be understood. The purpose of this study was to determine the existence and extent to which Kentucky women over 65 with the same stage of breast cancer receive breast-conserving surgery in different geographic regions, and to link geographic differences to differences in population characteristics, and the availability of health care resources for cancer treatment.