More than 1,500 students stripped down to bras, panties, boxers, briefs, thongs or pajamas for the twice-yearly run on the campus and in the surrounding town of Orange, Calif., The Orange County Register reported.
Students gathered at Attallah Piazza, and then took off -- many chanting, "Undie Run!" "Chapman!" and "USA!" -- and ran down the middle of Glassell Street to the Plaza Square and back.
The undie run is held at Chapman during the Wednesday of finals week in the fall and spring semesters.
Though Chapman doesn't sanction the event, university spokeswoman Mary Platt said, "Because of Chapman's unique location in the heart of Old Towne Orange, the university works closely with the city in assuring that the run takes place quickly and safely, with no danger to any people or property."
A historic fountain in the Plaza was broken during the fall semester run in 2008. Chapman paid $13,000 to fix the fountain and worked with city officials and student leaders to avoid further damage.
Now, the Plaza fountain and three others on the university campus are barricaded and nearly 30 police officers surrounded Plaza Park to make certain runners didn't stay there too long.