No backpacks or other large bags will be allowed along the 12K course during the May 19 race, which is being presented for the first time this year by the classified ad website Craigslist.
The maximum-size container or bag participants can carry is 8.5 inches by 11 inches by 4 inches, race officials said.
In addition, unregistered runners without race bibs will be removed from the course, organizers said. Existing bans on alcohol, floats, shopping carts, coolers and ice chests will still be in effect.
"We have been successfully and safely hosting the Bay to Breakers for more than 100 years, and with our city partners we have comprehensive security plans in place which we will continue to follow and adjust as circumstances warrant," race director Angela Fang said in a statement.
Police Chief Greg Suhr said, "We are asking observers and participants to be attentive on race day and report unattended items such as backpacks and packages -- if you see something, say something."
The April 15 bombings near the finish line of the Boston race killed three people and injured scores of others. Two Chechen brothers are believed to be responsible for the attacks. One has been killed, and the other, 19-year-old Dzhokhar Tsarnaev, is now in custody.
A moment of silence will be observed at the start of the Bay to Breakers race, which winds through the city from the Financial District to Ocean Beach. More than 30,000 people are expected to participate in the 102nd annual race this year.
More information about the race can be found online at www.baytobreakers.com or by calling (877) 234-8425.
