A man claiming to be one of the world's foremost experts on bull-running had a nasty surprise when he was hospitalised after being gored in the leg by one of the animals.
American Bill Hillmann has written a guide to bull-running in the northern Spanish town of Pamplona, which is famous for its annual bull-running festival, the Fiesta de San Fermin.
Ahead of this year's event, Bill tweeted this image showing off his expertise.
The 32-year-old from Chicago suffered the injury after being tripped over by another participant.
He sustained what could have been a life-threatening wound to his leg.
Had the bull's horn severed one of Bill's arteries he could have been in real trouble and he admits he was "worried if I'd survive" when he first saw the amount of blood he had lost.
Fortunately for Bill the injury was not as severe as he may have first feared and he told NBC News he was now "feeling good" and "not feeling any pain any more".
ITV News' Sue Saville reports on Bill's ordeal:
He describes getting gored as something that is par for the course for a bull runner.
As evidence of this, he points out that the man he considers the "greatest runner" of the current era, David Rodriguez, has been gored on three separate occasions in the last few years.
What's more, Bill insists his enthusiasm for bull-running has not been tempered by his injury, and he is looking forward to hitting the streets against "later in the summer".