Four people were injured Thursday as fighting bulls were released into the streets of Pamplona in the first bull-run of Spain's alcohol-fueled San Fermin fiesta.
One man suffered fractured ribs but the other three injuries were minor, according to AP.
Six massive fighting bulls and six agile steers were set loose in the lane ways and winding streets of the northern Spanish town, scattering daredevil runners dressed mainly in traditional white with red handkerchiefs around their necks.
"I've never actually felt something like that ever before in my life," British runner Jonathan Fieldhouse, 28, told AFP.
"One brushed past me, then all the rest came past," he added, his hands still shaking with adrenalin.
His 20-year-old brother Ben vowed to return next year. "The adrenaline pumps into you. It's unreal," he said.
The beasts and runners stampeded along a 848.6-metre (928-yard) course from a holding pen to Pamplona's bull ring, taking just two and a half minutes.
A festival organizer said the 2011 edition of the bull-run was "fast and clean."
"It is a very dangerous activity, you have to have a cool head," said Miguel Leza, 48, who was running for the 32nd consecutive year.
"You are up against a bull, a heavy animal which can kill."
The most recent fatality was in 2009 when horrified tourists looked on as a bull drove its horn in the heart, lungs and neck of a 27-year-old Spaniard.
The annual festival ends on July 14.