Criteria for record eligibility
In order for a performance to be ratified as a world record by the IAAF, the marathon course on which the performance occurred must be 42.195 km (26.219 mi) long, measured in a defined manner using the calibrated bicycle method and meet other criteria that rule out artificially fast times produced on courses aided by downhill slope or tailwind. The criteria include:
- "The start and finish points of a course, measured along a theoretical straight line between them, shall not be further apart than 50% of the race distance."
- "The decrease in elevation between the start and finish shall not exceed an average of one in a thousand, i.e. 1m per km."
In recognizing Kenyan Geoffrey Mutai's mark of 2:03:02 at the 2011 Boston Marathon as (at the time) "the fastest Marathon ever run", the IAAF said: "Due to the elevation drop and point-to-point measurements of the Boston course, performances [on that course] are not eligible for World record consideration."
Road racing events like the marathon were specifically excepted from IAAF rule 260 18(d) that rejected from consideration those track and field performances set in mixed competition.
The Association of Road Racing Statisticians, an independent organization that compiles data from road running events, also maintains an alternate marathon world best progression but with standards they consider to be more stringent.
Performances claiming world best or world record status on "point-to-point" courses such as the Boston Marathon have historically been rejected by USA Track & Field. Performances on these courses could be aided by slope and/or tailwinds.
Women's world record
The IAAF Congress at 2011 World Championships in Athletics passed a motion changing the record eligibility criteria effective January 2012, so that women's world records must be set in all-women competitions. The result of the change was that Radcliffe's 2:17:42 performance at the 2005 London Marathon would supplant the existing women's mark as the "world record"; the earlier performance was to be referred to as a "world best". The decision was met with strong protest in Britain, and in November 2011 an IAAF council member reported that Radcliffe's original mark would be allowed to stand, with the eventual decision that both marks would be recognized as "world records," the faster one as a "Mixed Gender" mark, the other as a "Women Only" mark.
Unofficial record attempt
In December 2016, Nike, Inc. announced that three top distance runners—Eliud Kipchoge, Zersenay Tadese and Lelisa Desisa—had agreed to forgo the spring marathon season to work with the company in an effort to run a sub-two-hour marathon, though a detailed plan to complete the marathon in 1:59:59 or faster was not released.
The Breaking2 event took place in the early morning of May 6, 2017; Kipchoge crossed the finish line with a time of 2:00:25. This time was more than two minutes faster than the world record, but was not an official world record. Among other factors, specialized pacers were used, entering the race midway to help Kipchoge keep up the pace.