One man was caught in the chest and legs when a large bull became separated from the pack on the slippery cobblestone streets leading to the bullring.
The bull, a Miura weighing 1,268 pounds, jerked the runner upward and then rolled him along the ground in the entrance to the ring. Miuras are the largest and most famous of Spain's fighting bulls.
The sixth running of the bulls at the annual festival was held two days after a 27-year-old man was gored to death, the first such fatality since 1995.
Medical services spokesman Dr. Fernando Boneta said five people suffered gorings, of whom two were in serious condition. One man was gored in the upper thorax.
Six others have bruising and all have been admitted for medical treatment.
The bull initially got a horn caught on a wooden barrier at a bend in the route, slipped and became embroiled in a three-animal pileup before resuming its gallop.
Bulls are at their most dangerous when the pack splits up, leaving individual animals disoriented and irritated by the large crowds traditionally clad in white, with red bandanna neckerchiefs and cummerbunds.
For more than 100 years thrill-seekers have accompanied the bulls from a pen outside the city walls on a dangerous, daredevil run to the bullring. In the afternoon, the bulls face matadors and almost certain death.
On Friday, Spaniard Daniel Jimeno Romero was gored in the upper chest and neck and was declared dead shortly after reaching the hospital.
By Associated Press Writer Alvaro Barrientos