Whether estimated or measured, mammographic or breast density, which may be subject to physiological and therapeutic variations, is widely viewed in the literature as an important factor of increased risk for breast cancer. A high breast density, the causes of which are being refined, would increase the relative risk of breast cancer four to six fold, even though some authors direct critics at methodological flaws supporting these results. Three-dimensional imaging will confirm or refute the available results. Meanwhile, radiologists and clinicians must remain vigilant in patients with high breast density.