U.S. couple Caelyn Casanova, left, and Johnny Nguyen, from Los Angeles, Calif., dance during the 2013 Tango World Championship salon category in Buenos Aires, Argentina, Monday, Aug. 19, 2013. (AP Photo/Victor R. Caivano)
The competition features 500 couples from 37 countries, including China and Pakistan, according to Prensa Latina.
It takes two to tango - but those two can be men or women in any combination.
Of the 500 couples in the 2013 competition, four are same-sex couples -- allowed to compete for the first time this year. Three of the couples are men and one of the couples is female, according to the Spanish-language publication, Clarin.com .