The competition has two parts: a first round and an eight-team final. Historically, there has been a semi-final round, but this has been eliminated as selection is now determined by time – the sixteen fastest nations during a pre-Olympic qualification period are entered. Since 1988, teams may enter up to six athletes for the event. Larger nations typically have two reserves runners in the first round in order to preserve the fitness of their top runners for the final. Heat runners of medal-winning teams receive medals even if they did not run in the final.
The Olympic records for the event were both set at the 2012 Olympic Games in London: the Jamaican men's team ran 36.84 seconds and the American women's team won with 40.82 seconds, both of them world records. The men's world record has been broken and equalled at the Olympics on numerous occasions. The record was set at six consecutive editions from 1912 to 1936, then five straight editions from 1956 to 1972. Since then, the men's Olympic final has been won in a world record time in 1984, 1992, and 2012. The women's world record has been similarly linked to the Olympics: the record was broken on the first three occasions it was contested as an Olympic event (1928 to 1936). It was then improved at six successive Olympics from 1952 to 1972. The women's world record at the 2012 Olympic Games ended the forty-year absence of such a feat.[1]
The United States is by far the most successful nation in the event. The country has won the men's race 15 times and the women's race on 12 occasions. The American men were dominant historically, accruing eight straight wins from 1920 to 1956, but have also logged numerous disqualifications (chiefly due to baton pass failures), including five straight from 2008 to 2024 (also in 1912, 1960, and 1988). The American women took four consecutive gold medals from 1984 to 1996. As of 2016, no other country has won more than three golds in the men's or women's event. Jamaica (four wins, nine medals), Canada (three wins, ten medals), Great Britain (two wins, fifteen medals) and the Soviet Union (two wins, eleven medals) are the next most successful nations.[2][3]
^On 25 January 2017, the Jamaican team was stripped of the gold medal due to Nesta Carter testing positive for the prohibited substance methylhexaneamine. The IOC requested that the IAAF modify the results, and, after CAS dismissed Carter's appeal, the medals were redistributed accordingly. Trinidad and Tobago team was advanced to gold, Japan to silver, and Brazil to bronze.
^On 18 February 2022, the British team was stripped of the silver medal due to CJ Ujah testing positive for the prohibited substances ostarine and S-23. After the medals were redistributed, Italy retained the gold medal, while the Canadian team advanced to silver and the Chinese team advanced to bronze.
