Three people were gored and a further two people suffered head trauma during the first day of Spain's best-known bull-running festival in the northern town of Pamplona on Sunday, the Red Cross said.
One man was loaded into an ambulance on a stretcher shortly after the dash through the medieval town centre's narrow streets to the bullring, which lasted two minutes and 41 seconds.
Thousands of runners, dressed head to toe in white, with bright-red neckerchiefs, gather every year for the traditional morning run, after which the animals are kept in the bullring until the afternoon's fights.
A total of 53 people were treated by the Red Cross. Runners often get injured at traditional bull-runs in Spain, but no one has died at Pamplona's San Fermin festival since Spaniard Daniel Jimeno was gored in the neck by a Jandilla bull in 2009.
This year, the bulls were from cattle breeder Puerto de San Lorenzo, whose bulls have been responsible for one goring in the past.
One person was gored on the opening day of the festival last year. The festival regularly stokes debate about the treatment of animals.
On Friday, protesters lay half-naked on the street with fake spears coming out of their backs to protest against what they see as cruelty.
The nine-day San Fermin fiesta, where the bulls are run every morning and killed in afternoon bullfights, draws around one million visitors annually.