We describe results from 284,503 mammographic examinations and associated diagnostic workups provided to medically underserved women in an ongoing nationwide breast cancer early detection program.We report the results of mammographic examinations and diagnostic workups on 230,143 medically underserved women 40 years old or older who underwent at least one mammographic examination from July 1991 through June 1995. Mammograms were obtained in hundreds of mammography and clinical facilities throughout the United States, including community health centers, health department clinics, private practitioners' offices, university based facilities, and mobile mammography units. Our analysis included rates of mammograms with abnormal findings (reported according to the categories of the American College of Radiology Breast Imaging Reporting and Data System), breast cancer detection rates, numbers of diagnostic procedures performed, stage and size distribution of breast cancers, and positive predictive value of mammo...