More than 100,000 demonstrators demanding an immediate end to the war in Vietnam massed on the Boston Common yesterday in the largest anti-war demonstration in New England history.

"Let's stop saving face and begin saving lives," said Sen. George S. McGovern (D-S.D.), the principal speaker at the rally. Urging immediate withdrawal, McGovern said, "To those who say this will cause a bloodbath in Vietnam. I say there is a bloodbath now."

Other speakers included Howard Zinn, professor at B.U., Rev. James K. Breeden of Roxbury, and Kay Hurley, of the South Boston Welfare Rights Chapter, Everett I. Mendelsohn, professor of the History of Science, introduced the speakers.

But the crowd seemed most enthusiastic about the address of Peter Camejo, of the Socialist Workers' Party, who said, "Watch out for the politicians who turn up now. They'll never march with you in the streets.

"There are people sitting in jail today because they were against this war. Let some politicians say something about that. Camejo said. "We're tired of rhetoric about ending the war that is really designed to keep this war going."

The crowd was so massive that many could not see the speakers' platform. The natural amphitheatre at the Beacon and Charles St. corner of the Common was jammed with demonstrators a half-hour before the speeches began at 3:40 p.m. And even when the speeches began, the last marchers had not yet reached the Common.

An estimated 15,000 demonstrators had gathered on the Cambridge Common at 1 p.m. for a rally before marching to Boston. George Wald. Higgins Professor of Biology, told the crowd. "I'll tell you how to get out of Vietnam-in ships. In a democracy, the government doesn't tell us; the President doesn't tell us: we tell them." As church bells tolled. Wald said. "Our national problem is that we're on our second amoral President."

Although the parade and rally wereorganized by former supporters of Sen. Eugene J. McCarthy (D-Minn.) and by the Student Mobilization Committee, more radical groups also participated. Members of the November Action Committee marched with National Liberation Front flags and wore red armbands. Members of SDS, which opposed the Moratorium, distributed pamphlets explaining their opposition.

The Common was filled with posters, signs, many colors of armbands, and black balloons. Demonstrators had lowered the American flag to half-staff.

As the march began at 1:40 p.m., parade marshals wearing yellow armbands tried to keep the crowd behind the lead banner, "On To Washington D.C. Nov. 15-Bring the Troops Home Now." A group of Vietnam veterans opposed to the war marched at the front, with arms linked, followed by members of the Harvard University Band playing the theme from "Exodus."

The two-hour march to the Common was peaceful and almost quiet. The demonstrators were spread out over a dozen blocks and were unable to sustain chants. Along Mass. Ave. near Central Square, thousands in the line of march waved peace signs at office workers, many of whom smiled and waved back. A radio station supplied several bushels of apples. When the demonstrators crossed the Harvard Bridge into Boston, they raised their arms in peace signs at police and press helicopters swooping low over them.

Policemen directed traffic along the line of march in Cambridge and Boston, but left control of the crowd largely up to the parade marshals. There was no violence, and many policemen smiled at the demonstrators as they passed.

The Cambridge group joined with others from Northeastern, M.I.T., and B.U. at the intersection of Mass. Ave. and Commonwealth Ave. in Boston. Along Commonwealth, dozens of windows were decorated with anti-war posters. Several young people leaned out of apartment windows and led chants of "Peace Now."

Motorists had been asked by Boston police to stay out of the downtown area after 1:30 p.m., and traffic was very light. It would have been virtually halted anyway, since the line of march stretched all the way from Mass. Ave. to the Common.

Folk and rock singers performed as the huge crowd marched into the Common, and an airplane drew an enormous peace symbol in the sky. Thousands who could not see the podium sprawled on the grass further back in the Common.