The first presidential debate between Donald Trump and Joe Biden takes place on Tuesday night between 9pm ET and 10.30pm ET (2am to 3.30am UK time).
It is being held on the campus of Case Western Reserve University in Cleveland, Ohio, and will be moderated by veteran journalist Chris Wallace of Fox News.
The now standard 90 minute debate will not have any commercial breaks and will feature six segments on different topics lasting 15 minutes each.
The candidates will each get two minutes to answer a question before Mr Wallace can open up the discussion.
A coin toss decides who answers the first question and who gives their closing remarks first.
The 2020 debates will follow the tradition of the past several election cycles with three presidential debates and one with the vice presidential nominees.
The first debate will be followed on 7 October by the vice presidential debate between Mike Pence and Kamala Harris in Salt Lake City, Utah.
Then the two remaining presidential debates will then take place on 15 October in Miami, Florida, and on 22 October, in Nashville, Tennessee.
The Commission on Presidential Debates has organised the election debates for more than three decades.
Each debate has been 90 minutes in length, since moving from one hour in 1980.
Historians say that modern debates can be traced to a series of Illinois Senate debates held by Abraham Lincoln and Stephen Douglas in 1858.
Both men attended seven debates, which each lasted three hours.
In 1940 Wendell Wilkie became the first 20th century candidate to challenge his opponent to a debate but then-president Franklin Roosevelt refused to take part.
The first televised presidential debate took place in 1960, between John Kennedy and then-vice president Richard Nixon, with Kennedy going on to win the White House.
Lyndon Johnson refused to debate Barry Goldwater in 1964 and there was not another debate for 16 years.
In 2016 the first debate between Donald Trump and Hillary Clinton became the most watched ever with 84 million viewers.
It beat the1980 debate between Ronald Reagan and Jimmy Carter, which saw 80.2 million viewers tune in.
