The Lilac Bloomsday Run has had over 40,000 participants every year since 1986. Race participation peaked in 1996 with 61,298 registered participants. The number of registrants in 2008 was 47,528. Lineth Chepkurui set an unofficial 12 km world record in the 2010 women's race.[nb 1]
^The International Association of Athletics Federations, the international governing body for the sport of athletics/track and field, does not recognize world records or world bests in either an indoor or outdoor 12 km. The Association of Road Racing Statisticians does recognize a world record in the outdoor 12 km, however, their record keeping rules state: "A record quality course is defined as having not more than 1 m/km net drop between the start and finish and not more than 30 percent of the race distance separation between that start and finish, e.g. not more than a 3 km separation for a 10 km race [or 3.6 km for a 12 km race]. Records will only be accepted for record quality courses." Per ARRS standards, the course for the Lilac Bloomsday Run fulfills these conditions. Although Chepkurui ran a 38:07 two weeks later on May 16, 2010 at the Bay to Breakers (presumably the fastest 12 km ever for a woman), the course is not considered a "record quality course" in that the start and finish are separated by approximately 10.5 linear kilometers.