The Red Cross says three men—two Americans and one Spaniard—were gored Friday at the opening run of the bull-running festival in the northern Spanish city of Pamplona.
The aid agency said the 46-year-old Spaniard suffered serious injuries and had undergone surgery to his head and leg.
Hospital officials said the Americans' injuries were not as serious, with one being gored in the abdomen, while the other had been gored in the scrotum.
The bulls in Friday's run were from the Cebada Gago ranch, known to produce fierce bulls responsible for causing the most injuries in the week-long San Fermin festival.
The festival was immortalized by Ernest Hemingway in his 1926 novel The Sun Also Rises.