This article reports the results of mammography screening among socioeconomically disadvantaged women in Bronx, NY using a federally funded low-cost or no-cost cancer screening service. The New York State Department of Health provided funds for the uninsured through the Bronx Breast Health Partnership. All women < or = 40 years underwent screening mammography using both a mobile van unit and hospital-based mammographic x-ray unit, both American College of Radiology (ACR) accredited. Return visits were coordinated by a follow-up clinic at Montefiore Medical Center using a patient navigator who acted as an advocate for patients with abnormal screening findings. The overall detection rate of 12.9 per 1000 women screened was significantly higher than the New York State detection rate of 6 per 1000 and 5.1 per 1000 nationally. Availability of a patient navigator was an essential factor in the effectiveness of the work-up of problem cases. Low-cost or no-cost breast cancer screening programs can improve the availability, accessibility, acceptability, and utilization of mammography among underserved and uninsured women who are least likely to be screened otherwise.