Background: In response to concerns about the limited sensitivity of mammography among women with dense breasts, 32 states have enacted laws to inform patients about these limitations and recommend adjunctive screening tests such as breast ultrasound. Inform mandate laws represent a novel approach to ensure awareness of technologies that have not yet been proven to affect health outcomes. We evaluated the effect of inform mandate laws on utilization of adjunctive screening, biopsy and diagnosis of incident breast cancer. Methods: Using blinded administrative claims data from anonymous insurers conducting business in the United States, we included women age 40-59 who underwent screening mammography in 2015. We classified beneficiaries according to receipt of screening mammography in a state with an inform mandate law. Receipt of screening or diagnostic ultrasound, breast biopsy, and incident breast cancer within nine months of screening mammogram was identified from claims. Logistic regression was used to evaluate the association between inform mandate laws and receipt of screening ultrasound, diagnostic ultrasound, biopsy, and cancer detection, while adjusting for age and type of health plan. Robust variance estimates accounted for clustering by state. Results: Our sample included 1,595,864 women who received a screening mammogram in 2015. Of these women, 58.2% were living in a state with an inform mandate law in place at the time of index mammogram. The adjunctive screening ultrasound rate was 3.1% among women in inform mandate states vs 1.4% in non-mandate states. After adjustment, residence in an inform mandate state was associated with significantly higher odds of adjunctive screening ultrasound (OR 2.22, 95% CI 1.14-4.34). In contrast, inform mandate status was not associated with receipt of diagnostic ultrasound, breast biopsy, or cancer detection. Conclusions: Women residing in states with breast density inform mandate laws are more likely to receive screening breast ultrasound. However, there was no significant relationship between inform mandate laws and utilization of other adjunctive tests or the likelihood of cancer detection.