Eduardo Frei Montalva, who proclaimed a "Revolution in Liberty" while serving as president of Chile from 1964 to 1970 and who saw the collapse of his nation's vaunted democracy three years after leaving office, died yesterday at the Santa Maria Clinic in Santiago. He was 70.

His death was attributed to an abdominal infection arising from an operation Nov. 18 for a hernia. He left the hospital several days later, but returned on Dec. 5 and his condition worsened.

Because of sweeping social changes that Mr. Frei initiated, Presidents Kennedy and Johnson looked to him as an initiator of rapid development without violence or repression. But the Chilean electorate's quest for change, which he whetted without fulfilling, soon led to rejection of his Christian Democratic Party in favor of Marxist Socialist Salvador Allende. Political polarization and a violent military coup followed quickly.

A somber and haughty politician, Mr. Frei looked the part of a European statesman. His father was Swiss-born and his mentor was French philosopher Jacques Maritain. As Mr. Frei pressed policies of agrarian reform, income redistribution and mass participation in decision-making, he did it with a careful phrasing more akin to a college professor than a revolutionary.

In an interview in 1966, at the height of hopes for his reform-revolution, he admonished: "I offer neither immediate solutions nor immediate prosperity, but sacrifice in the present for prosperity in the future."

If he lacked Latin charisma and the politician's gift of hyperbole, he nonetheless inspired voter loyalty. For many Chileans, it survived even that deadly embrace Washington often bestows on those it esteems in the Third World: revelation that the CIA had backed his presidential campaign.

During the turbulent Allende years, former president Frei came to despise his successor and erstwhile close friend. When the two had contested for the job in 1964, Mr. Frei referred to his opponent as "an honorable and hard-working man as well as a first-rate parliamentarian."

In 1970, Mr. Frei had faced down schemers determined to prevent Allende's accession after his popular-vote victory that year. But 15 months into Allende's term, the embittered Christian Democrat said Allende was "dedicated to creation of a totalitarian dictatorship."

In early 1973, at what should have been the midpoint of Allende's term, Mr. Frei easily won election to the Senate. He dominated the ever more intransigent opposition and acceded to the coup by the time the military decided to move in September of that year. The generals then killed or exiled most of the political leadership, yet they dared not act against Mr. Frei as he shifted -- too slowly, in the eyes of his critics -- into the antimilitary camp.

After the coup in 1973 that ended Latin America's longest-running democratic experiment, Mr. Frei retired to his unpretentious house on Hindenburg street in suburban Santiago with his wife, Maria, and occasional visits of his seven grown children. He had lived there even as president, rejecting an apartment in the government house, La Moneda.

In 1978, the military called a plebiscite in reaction to a U.N. condemnation of Chilean human-rights violations. Mr. Frei led what little opposition campaigning that the junta's rules allowed. President Augusto Pinochet refused Mr. Frei's challenge to public debate, reportedly saying that for him to confront the urbane intellectual with words would be equivalent to Frei accepting a duel with pistols. Gen. Pinochet is a marksman.

The plebiscite, posed in terms of "reaffirming" Chile's legitimacy, was termed unfair by the State Department and sharply criticized elsewhere. In any case, it carried. Supporters of the junta topped off that first voting day in five years by gathering outside his house to shout insults and obscenities.

Eduardo Frei Montalvo was born on Jan. 16, 1911, in Santiago. His public career began in the rough-and-tumble politics of the 1930s following his graduation from the law school of Santiago's Catholic University. He and other student leaders, unhappy with the limited democracy afforded by the traditional parties, and opposed to the communism or fascism then proposing alternatives, formed the National Falange.

This precursor of the Christian Democratic Party had nothing to do with the fascist Falange in Franco's Spain. In 1957, Mr. Frei transformed the organization into the Christian Democratic Party. By 1964, the party was strong enough not only to provide candidate Frei with an absolute majority, unprecedented in modern Chile, but a majority in the lower house of Congress as well.

As always in Chile, the economy lurched up and down with the price of copper, the main export, and growth was minimal in Mr. Frei's last years in office. Much of the electorate moved leftward, and this provoked a revival of the right that he had coopted in 1964. As a result, the party's candidate in 1970, Radomiro Tomic, ran last in a three-way race won by Allende with 36 percent of the vote.

In 1973, when Mr. Frei was moving his party into more implacable opposition to Allende, a Senate Foreign Relations subcommittee in Washington conducted an investigation that led to revelations of CIA aid to the Christian Democrats in 1964 -- up to $20 million contributed to the campaign, according to participants-- under President Johnson.

The headlines in Santiago were withering and the party's denials insistent. Mr. Frei refused to comment. There is considerable doubt that so much money reached the party coffers -- for instance, a slick daily described by the U.S. officials as one product of the outlay was unknown in Chile even to archivists -- let alone that it affected the result.

Because of the military takeover in 1973, Mr. Frei never had another chance to test his electorate on the ultimate impact of the revelations that year.