The 2000 Summer Olympics saw the first appearance of the triathlon. 48 women and 52 men competed in separate triathlons. The distances used were the "international" or "standard" ones, with a 1.5 km (0.93 mi) swim, 40 km (25 mi) cycle, and a 10 km (6.2 mi) run. The 2004 triathlon was identical to the first in distance, but the 100-athlete quota was evened between 50 women and 50 men. The quota was further increased to 55 women and 55 men for the 2008 Beijing Olympics and remained the same for London 2012. In London, the women's triathlon took place on Saturday 4 August, with the men's event on Tuesday 7 August.
There are five ways for NOCs to earn spots in the triathlon. NOCs can earn a maximum of three spots, though only eight nations may earn that many. Nations beyond that may earn only two spots.
The first five spots go to the winners of the five regional qualifying tournaments. Three more spots go to the top three triathletes of the most recent Triathlon World Championships, though any athlete that won a regional tournament is skipped in that determination. The next 39 places go to the NOCs of those athletes highest in the ITU ranking (again, skipping those athletes that have already qualified in the first two methods). A forty-eighth place is awarded to the host country if it has not already received a spot, or to the next highest ranked athlete if the host country has. Two places are awarded by the Tripartite Commission. In the end, further five places are distributed to the NOCs without any quota through the ITU Points List, with one place for each continent.
The Olympic triathlon is composed of two medal events, one for men and the other for women. Both use the same distances of 1.5 km, 40 km, and 10 km. Mass starts are used and drafting is allowed during the cycling phase.
Because of the variability of courses, official records are not kept for the triathlon. This rule applies to Olympic games as well.