On September 8, 2015, the Department of Health and Human Services (HHS) proposed regulations to implement Section 1557 of the Affordable Care Act (ACA), which prohibits discrimination in health coverage and care based on race, color, national origin, age or disability, and, for the first time sex. This Issue Brief provides a technical summary of Section 1557 and the proposed rule and highlights new protections and provisions included in the law and rule . Notably, Section 1557 is the first federal civil rights law to prohibit discrimination on the basis of sex in health care. Moreover, the proposed rule extends the definition of sex discrimination to include discrimination on the basis of gender identity (but does not explicitly include sexual orientation). In addition, the proposed rule establishes regulations related to the provision of language assistance services based on long-standing HHS policy guidance. This brief does not assess the implications of the proposed rule.