The United States Department of Justice Antitrust Division is a law enforcement agency that enforces the U.S. antitrust laws. It has exclusive jurisdiction over American criminal antitrust prosecutions, and shares jurisdiction with the Federal Trade Commission (FTC) over civil antitrust cases. The Antitrust Division often works jointly with the FTC to provide regulatory guidance to businesses.
The head of the Antitrust Division is an Assistant Attorney General for Antitrust (AAG-AT) appointed by the President of the United States. Since September 2017, the position of Assistant Attorney General for Antitrust has been held by Iranian-American lawyer Makan Delrahim.
On February 25, 1903, Congress earmarked $500,000 for antitrust enforcement. On March 3, 1903, Congress created the position of Antitrust AG, with a salary to be paid out of the funds earmarked for antitrust enforcement. The 1904 DOJ Register identified two professional staffers responsible for enforcement of antitrust laws, but it wasn't until 1919 that the Division was formally established. AG A. Mitchell Palmer "effected the first important reorganization" of DOJ since it was first established in 1870. Palmer organized DOJ into divisions, and placed the AtAG "in charge of the Anti-Trust Division." Palmer's annual report for the fiscal year ending June 30, 1919 contained the first public statement that DOJ had a component called the "Antitrust Division." 
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The Antitrust Division is overseen by an Assistant Attorney General. The Assistant Attorney General is assisted by six Deputy Assistant Attorneys General (DAAG) who each oversee a different branch of the Division. One of the DAAGs holds the position of "Principal Deputy," that is "first among equals," and "will typically assume the powers of the Assistant Attorney General in the Assistant Attorney General's absence."
The closure of four of the Antitrust Division's criminal antitrust offices in January 2013 generated significant controversy within the Division and among members of Congress. The Attorney General posited that the closure of these offices will save money and not negatively affect criminal enforcement. A significant number of career prosecutors have voiced contrary opinions, noting that the elimination of half of the Division's criminal enforcement offices will increase travel expenses and diminish the likelihood of uncovering local or regional conspiracies.