Most Americans clearly believe that routine screening mammography is beneficial. Given its widespread acceptance, it is useful to consider what the downsides of mammography screening are so that patients are fully informed in the decisions they make. This article lists some less well-recognized risks of mammography, such as false negatives and their accompanying false reassurance, as well as the direct and indirect costs to women and society. Three important downsides-radiation hazard, overdiagnosis of breast cancer, and the paradoxical increase in breast cancer mortality observed in screened women compared to controls age 40-49 years-are addressed. The article also considers the reasons that women are poorly informed about the downsides of mammography. There is, however, agreement that early diagnosis and treatment are important, and that new methods to reduce breast cancer deaths must be sought.