They are using equipment designed in the 1920s to retrace the steps of George Mallory and Andrew Irvine's climb up Mount Everest, from which the duo never returned, the BBC reported Monday.
The two British climbers disappeared just short of the summit in 1924.
The current climbers are trying to figure out if the two men actually reached the summit nearly 30 years before climbers Edmund Hillary and Tenzing Norgay, now regarded as the first to scale Everest's heights.
The last sighting of Mallory and Irvine was reported a few hundred meters short of the summit, right before bad weather closed in.
Close to where the climbers were last seen in 1924 lies a 40-meter high, near-vertical rock face called the Second Step, which reportedly is the hardest part of the climb.