There is now considerable concern that universal access to health care within realistic resource constraints requires some sort of cost-effectiveness analysis of given medical procedures and interventions. One such intervention is routine mammographic screening for breast cancer. Here, we report preliminary results from an ongoing project to conduct a systematic and comprehensive review and comparison of the published cost-effectiveness analyses of screening for the early detection of breast cancer. We examine 16 such studies, and compare two studies in detail to explain how differences in assumptions and in consideration of down-stream effects have caused the published results for apparently comparable breast cancer screening programs to span a broad range.