Low income and minority women continue to have relatively low breast cancer screening rates. Since physician recommendation is one of the most important determinants of mammography participation, we aimed to characterize the breast cancer screening knowledge of primary care providers serving a socially disadvantaged population. The study was conducted at the Adult Medicine Clinic of Seattle's county hospital. All attending physicians, resident physicians, and mid-level practitioners were asked to complete a questionnaire in the spring of 1995. Forty-nine of 52 (94%) eligible providers completed the survey. The respondents generally agreed with published guidelines for screening mammography use. In contrast, they had relatively low levels of knowledge about breast cancer risk factors and the effectiveness of other breast cancer screening methods. Additionally, providers tended to over-estimate their breast cancer screening knowledge and skills. For example, 69% believed that they could answer patients' questions about mammography, but only 23% were aware of Medicaid's reimbursement policy for the procedure. For some variables, attending physicians were no more knowledgeable than resident physicians. Our results reinforce the need for increased preventive care training in medical schools and primary care residency programs. Educational programs for providers serving disadvantaged populations might usefully focus on pragmatic issues such as institutional costs and public payor reimbursement policies.