Annual mammography, in combination with clinical breast examinations, can reduce mortality from breast cancer. However, surveys of both patients and physicians suggest that mammography is underutilized. This study examined whether physicians' reported breast cancer screening practices and barriers to mammography varied with patients' age. Data from 576 primary care physicians (internal medicine, family/general practice, and obstetrics/gynecology) who participated in a mailed statewide survey were analyzed. Physicians reported screening elderly women significantly less often than younger women, regardless of family history of breast cancer. With the exception of medical specialty, physicians' demographic and practice characteristics were not associated with reported screening practices. However, physicians' knowledge and beliefs about breast cancer in older women were associated with reported screening practices. When analyzing barriers to ordering mammography, cost to the patient was viewed as a barrier for women of all ages, and pain was viewed as a greater barrier for younger women; otherwise, physicians consistently believed that their elderly patients faced considerably more barriers compared with younger women. Further investigation is required to examine why primary care physicians report age-related differences in both breast screening and barriers to mammography.