The protesters wore helmets and harnesses as they made their way up the cables running next to the south tower of the famed span. The climb had the group suspended about 150 feet above traffic.
Reached by cell phone as he dangled from the bridge, demonstrator Laurel Sutherlin said he was worried that the torch's planned route through Tibet would lead to more arrests and Chinese officials would use force to stifle any visible dissent.
"The leaders of China have said they'll maintain order at all costs, and we know what that means -- bloodshed and violent oppression," he said. "If the IOC allows the torch to proceed into Tibet they'll have blood on their hands."
The organizers behind Monday's action said they'll remain faithful to their mission of protesting without violence when the torch relay takes place Wednesday here, its only North American stop, despite the disruptive action on the bridge.
They said they wanted to take full advantage of the moment in the international spotlight to get their message out.
"This is a life or death situation for Tibetans," said Yangchen Lhamo, an organizer of Monday's banner hanging who is on the board of directors of Students for a Free Tibet.
Mary Ziegenbien, a spokeswoman with the California Highway Patrol, said authorities would not try to go get the protesters out of concern for their safety.
"We don't want to put their lives in danger by going and grabbing them off the suspension cables right now," she said.
The torch's path around the globe already has been marked by protests against China's policies toward Tibet and Sudan.
In Paris, organizers canceled the final leg of the Olympic run after chaotic protests, snuffing out the torch and putting it aboard a bus.
Rallies, vigils and news conferences related to the torch's arrival have taken place in San Francisco almost daily for the past several weeks. More are planned over the next two days in anticipation of the torch's arrival.
About 80 torchbearers will carry the flame on a six-mile route along the San Francisco Bay.