Monday's events mark the 38th anniversary of Roe v. Wade, the 1973 Supreme Court ruling that legalized abortion.
Participants in the 27th annual Pro-Life Prayer Walk are scheduled to meet at St. Nicholas Church, at Lincoln Avenue and Sherman Street, and walk eight blocks through downtown to City Hall.
The prayer walk also coincides with the 37th annual March for Life in Washington, D.C., which draws hundreds of thousands of pro-life activists.
"We want people to remember that what's involved is the life of a child. I think a lot of people don't realize that or they forget it," said Hubert Lipinski, an organizer of the Los Altos walk.
"The net result is that a quarter of the generation that is to be born is lost to abortion. It's quite disconcerting," he said.
The Prayer Walk is not intended to be a political statement but rather a moral one, Lipinski said.
"It's really a religious event. It has a very strong religious tone," he said.
Pro-choice activists will be marching alongside the prayer walk but on the opposite side of the street, organizers said.
Activists are scheduled to meet at the Los Altos Youth Center at 1 N. San Antonio Road at noon.
The pro-choice rally was started in 2002 by the American Association of University Women in response to the prayer walk.
"We felt there needed to be a counterpoint to give people another option," organizer Lois Rosenblum said.
The pro-choice rally is a social statement, Rosenblum said.
"We stress education - educating young women about their health," she said.
Despite the differing opinions and the close proximity of the two rallies, both sides said they don't expect any problems.
"It's always been a very peaceful, safe environment," Los Altos police Capt. Andy Galea said.