The 46-year-old man from Paisley suffered head injuries after falling during the daily 8am run through the streets of Pamplona in northern Spain.
He was one of seven people injured during the fifth of the eight runs. The Scot was not fully named and only his initials - A. R. - were released. Hospital bosses said he had suffered "light head trauma".
His hospitalisation took the tally of injuries in this year's runs so far to 28.
Fifteen people have been killed at the annual festival since records began in 1911.
Virtually all the revellers wear red and white during the Running of the Bulls festival which lasts nine days. The six bulls used for yesterday's run were from the Jandilla breed. Bulls from the breed have gored 27 runners in previous years.