The format is brutally simple. Each day brings a morning stage of roughly 75 kilometres and an afternoon stage of about 45, run over five days for a total course somewhere between 500 and 600 kilometres. Riders move as a managed group, always travelling between a front convoy of support vehicles and a rear one led by a sweep vehicle. Fall behind the sweep and you are pulled from that stage and driven to camp, though you can restart the next morning. To stay ahead you must hold a minimum average speed across terrain that does everything it can to slow you down. Water stops appear at intervals, and every rider must halt and drink; at the start and end of each stage their body weight is recorded, a blunt and effective way to catch dangerous dehydration before it catches them. Beyond the water, they are on their own.

In the early years riders rode rigid mountain bikes with skinny tyres and spent much of the desert pushing rather than pedalling, shoving their machines up the soft faces of the dunes. The classic route ran the firmer ground of the Rig Road and the Birdsville Track. Then, after 2009, the fat bike arrived, with tyres four inches wide and more that floated over sand once thought unrideable. Suddenly riders could climb even steep dunes without dismounting, and the event transformed. Today fat bikes dominate, and organisers can route the race down harder lines like the French and WAA, where the dunes rise sharper and more often than on the old classic course.

The Challenge is open to all ages and abilities, and the start list reads like a slice of ordinary life: a police officer, a coffee shop owner, an IT manager, all out in the same dunes. The desert treats them equally, which is to say harshly. Every rider who completes every stage earns the coveted 100% medal, but on average only about 36 percent of starters manage it. In 2008 the desert won outright and not a single rider finished the course; in 2016, by contrast, no one was swept at all. Weather writes much of each year's story. Searing dry heat, sudden flooding, even bushfires have forced the race onto alternative ground, and in 2020 the global COVID-19 pandemic cancelled it for the first time in its history.

The race began in 1987 and has been run ever since by a band of volunteers, formally incorporated in South Australia as the not-for-profit Desert Challenge Inc. Its founding figures, including organisers Jack and Mary Mullins in the early years and later Rod and Loz Townsend, steered it through decades and several charity partners. Since 2008 the proceeds have gone to the Royal Flying Doctor Service, the airborne medical lifeline of the outback, raised through rider fundraising, a post-race auction, and a running tally of light-hearted fines. The sums have climbed past 350,000 dollars. It is a fitting beneficiary: out here, where the nearest hospital can be hundreds of kilometres of dune away, the Flying Doctor is the difference between a bad day and a fatal one, and the riders crossing the Simpson know it better than most.