Congress remains deeply divided over implementation of the Patient Protection and Affordable Care Act (ACA), the health reform law enacted in March 2010.1 Since the ACA's enactment, lawmakers opposed to specific provisions in the ACA or the entire law have repeatedly debated its implementation and considered bills to repeal, defund, delay, or otherwise amend the law. To date, most of this legislative activity has taken place in the House, which reverted to Republican control in 2011. Over the past four years, the Republican-led House has passed numerous ACA-related bills, including legislation that would repeal the entire law. But there has been far less debate in the Senate, which remained under Democratic control through 2014. Most of the ACA legislation that passed the House during this period was not considered in the Senate. However, a few bills to amend specific elements of the ACA that attracted sufficiently broad and bipartisan support were approved by both the House and the Senate and signed into law. Now that Republicans control both chambers of Congress, opponents of the ACA see new opportunities to pass and send to the President legislation that would change the law. In addition to considering ACA repeal or amendment in authorizing legislation, some lawmakers have used the annual appropriations process in an effort to eliminate funding for the ACA's implementation and address other concerns they have with the law. ACA-related provisions have been included in enacted appropriations acts each year since the ACA became law. In October 2013, disagreement between the House and Senate over the inclusion of ACA language in a temporary spending bill for the new fiscal year (i.e., FY2014) resulted in a partial shutdown of government operations that lasted 16 days. This report summarizes legislative actions taken to repeal, defund, delay, or otherwise amend the ACA since it was signed into law. The report is divided into two sections. The first section focuses on authorizing legislation, and the second section discusses appropriations bills. While a detailed examination of the ACA itself is beyond the scope of this report, a brief overview of the ACA's core provisions and its impact on federal spending is provided.2 This material is included to help provide context for the discussion of ACA legislative activity that follows. This report is updated periodically to reflect legislative and other developments.