Objective: The purpose of this study was to determine the prevalence, medical services and treatment utilization, and costs associated with breast cancer in a socioeconomically underprivileged population covered by a state Medicaid fee-for-service (FFS) program. Methods: We analyzed the West Virginia (WV) Medicaid FFS administrative claims data for women recipients 21-64 years of age enrolled continuously in the program during the calendar year 2005. Breast cancer-related medical services and treatment use and costs were calculated for women recipients with breast cancer. The excess burden of breast cancer was calculated by comparing the all-cause healthcare utilization and costs among women recipients with breast cancer to a matched control group of women recipients without breast cancer. Healthcare costs incurred during the 1-year study period were calculated from the perspective of state Medicaid. Cost estimates in the study excluded out-of-pocket expenses and indirect costs of breast cancer. Results: In 2005, the prevalence of breast cancer in the WV Medicaid FFS program was 22.7/1000. More than 98% of breast cancer-related medical services utilization occurred in the office setting. Approximately 73% of women recipients with breast cancer had at least one claim for breast cancer treatment, with hormone therapy being the most common (55.1%) treatment. The all-cause healthcare costs were significantly higher for women recipients with breast cancer compared to those without breast cancer ($16,345 vs. $13,027, p<0.001). Conclusions: Consistent with our expectations, breast cancer diagnosis among women recipients in the WV Medicaid FFS program was found to be associated with higher all-cause healthcare use and costs compared to women recipients in the matched control group. The excess cost burden associated with breast cancer could be attributed to higher office visit, emergency room visit, and prescription medication use among recipients with breast cancer.