The "Vierdaagse" is an annual IML walk that has taken place since 1909.

Based at Nijmegen since 1925, it now takes place in the third week of July.

In 2016 it celebrated the 100th edition (reflecting that the marches were curtailed during the two world wars). Originally a military event with a few civilians, it now is a mainly civilian event. Numbers have risen in recent years, with over 40,000 taking part annually, including about 5,000 military, and is the world's largest walking event. Due to possible congestion on the route, since 2004 the organisers have limited the number of participants. Many take part every year, including several who have taken part in over 60 annual marches.

Each day of the marches is named for the biggest town on the daily route. Tuesday is the day of Elst, Wednesday the day of Wijchen, Thursday the day of Groesbeek and Friday the day of Cuijk. The routes always remain the same unless there is a specific need to change. This happened in 2007 when the walkers went along the Waalkade, beside the River Waal, on Wednesday for the first time due to congestion on the original route. The 2006 march was the first to be cancelled since World War II, after extreme heat caused thousands of drop-outs and two deaths during the first day's march. Following the 2006 cancellation, it was decided that the organising committee would adjust the start time/distance/finish time to manage the event, instead of outright cancellation. The 2016 centenary event responded to unusually hot conditions by adjusting starting times and/or increasing the valid finishing time to reflect the difficulty of the course. Due to the coronavirus pandemic, both the 2020 and 2021 Vierdaagse events were cancelled.

On Fridays of the event, as participants near the finish, the public presents walkers with gladioli, a symbol of victory since Roman times, when gladiators were likewise showered with these flowers. The entry into the city and towards the finish, along the St. Annastraat, is for that reason called Via Gladiola during the event. As far as a week ahead of that Friday, people will reserve spaces alongside the Via Gladiola by placing chairs and even couches. The finish is broadcast on Dutch television.

Military participation

Originally primarily a military training event for the Dutch infantry, since 1928 the Vierdaagse has attracted armed forces personnel from other countries, when Germany and Norway sent army teams. Military teams increased greatly after 1945. The U.S. Army first took part in 1947, the United Kingdom in 1950 and Canada in 1952, with service contingents now also regularly travelling from Germany, Scandinavia, Switzerland and others. In recent years military participants, including Dutch personnel, have numbered approximately five thousand, most marching in teams of between eleven and thirty members. They are required to carry at least 10 kilogrammes of dead weight (if they are over 18 years of age), although this requirement can be waived when temperatures get too high, as happened in 2006 and the last day of the 2014 march. Military teams have their own route, (40 km), starting in the military camp Heumensoord, just south of Nijmegen, which is built for the event every year.