Last year a 62-year-old local man died after spending months in a coma, bringing the total of bull-run deaths to 15 since 1910.
Runners come to what they say is one of the few places where no law or fear of litigation stops them risking their lives and experiencing the delirium that comes with escaping in one piece.
"I'm seeking an adrenalin rush ... In today's world, being able to run with bulls, in Australia the liability insurance [would stop it]. But here tradition overrules all that politics ... They seem to understand that you're big enough to make your own decision," said Mick Russell, a 22-year-old builder from Shepperton, Australia.
Pamplona's authorities did try to stop locals running with the bulls for centuries but in 1867 they gave up and made it an official part of the festival.
"It's something to make you feel alive ... I have to feel the adrenalin, I want a near-death experience," said Bobby Moran, 23, an accountant from Melbourne.
Caracas fireman Hugo Sanchez uses a fair bit of adrenalin in his day job, but says he likes to experience a rush that other people's lives do not depend on. He came to Pamplona this year for the first time and plans to come back for as long as he can.
"Pure adrenalin ... like everything beautiful in this life," Sanchez said.
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