The proliferation of legislation on breast density, requiring direct notification of a patient if she has dense tissue on mammography, has resulted in a highly charged debate. Early legislation stemmed from a grassroots patient advocacy group (AreYouDense, Inc.) led by Nancy Cappello, PhD. Dr. Cappello is a breast cancer patient who believes her delayed diagnosis resulted from the masking effect of her dense breast tissue. The thrust of the advocacy group is summarized in an article that Dr. Cappello wrote in the Journal of the American College of Radiology titled, “Decade of ‘normal’ mammography reportsdthe happygram.” In this article, Dr. Cappello discussed the blissful ignorance of being told she had a normal mammogram year after year without being aware of the reduced sensitivity of the examination due to her dense tissue. She has a valid point. Patients should be more aware of the reality of reading mammograms. Mammography is not a perfect test. The ability to identify some cancers in dense breasts is a difficult and sometimes impossible task. Dr. Cappello went on to say, “My radiologist knew I had dense breasts. My doctor knew I had dense breasts. The only person who didn’t know was me: the woman with the dense breasts.” Advocating for patient education and awareness became her mission. As a consequence of the massive lobbying efforts of such advocacy groups, legislation was passed in Connecticut in 2009 and has been passed in 14 subsequent states. Although only 15 states have these laws in effect, most of them are heavily populated states, accounting for over half of the female population of the United States. Based on nationwide data, women with breasts considered dense under the law account for approximately 50% of women undergoing screening mammography. Thus, density notification legislation is already affecting many millions of American women. This issue has been divisive in the medical community: some physicians perceive the legislation to be beneficial, others see it as reasonable, and still others perceive it to be frankly harmful.