David Dellinger, 88, a lifelong radical pacifist and one of the Chicago Seven antiwar demonstrators during the 1968 Democratic National Convention, died of pneumonia May 25 at the Montpelier, Vt., retirement home where he lived. He had Alzheimer's disease.

Mr. Dellinger, who had been protesting since the 1930s, was the oldest of the seven (originally eight) Vietnam War protesters charged with conspiracy and inciting to riot after a massive demonstration in the streets and parks of Chicago turned violent. Among the bearded, beaded and wild-haired defendants, he was balding and wore a coat and tie. He and Abbie Hoffman, Jerry Rubin, Tom Hayden and Rennie Davis were convicted of inciting a riot, but the convictions were overturned on appeal.

One of his four surviving children, Michele McDonough, said yesterday that Mr. Dellinger remained actively engaged in issues until just a few years ago. The "last real trip he made," she said, was three years ago when he hitched a ride to demonstrations in Quebec City against the creation of a free trade zone in the Western Hemisphere.

"He felt this is one of the most important times to be active," she said. "He was working on a wide range of things: prisoners' rights, supporting a living wage, demonstrating and writing about foreign policy of this government."

Mr. Dellinger had been to court, to jail and to prison long before the '60s, although that is the era with which he is most identified. He supported union organizing drives in the 1930s and civil rights in the 1950s. He was jailed so often that he had lost count.

"I went from Yale to jail," he said, "and got a good education in both places."

He refused to register for the draft during World War II, even though he could have had a deferment because he was studying for the divinity at Union Theological Seminary. The courts were not in a mood to hear his critique of the "strategic disagreement" between the U.S. imperialists and the Third Reich; he was sent to federal prison in Danbury, Conn., for a year and a day. When he got out, he still refused to register, and was sent to the maximum-security prison at Lewisburg, Pa., where he staged hunger strikes and spent time in solitary confinement. Three years later, he was released.

Mr. Dellinger continued to protest -- against nuclear testing, against the bomb, against the Korean War, for prisoners' rights and for Puerto Rican independence. A critic called him "the Kilroy of radical politics," who appeared at nearly all the big demonstrations. He worked with the radical Catholic priests, the Berrigan brothers, to write a "declaration of conscience" to encourage resistance to the draft, and he was one of the organizers of the National Coordinating Committee to End the War in Vietnam, which staged the huge antiwar marches in Washington in 1970.

He made two trips to China and North Vietnam in 1966 and 1967. He marched on the Pentagon repeatedly. After the Chicago Seven trial, North Vietnam decided to release a few U.S. prisoners of war, and its leaders asked Dellinger, among others, to come to Hanoi to escort them back to the United States, which he did.

At the 1969 trial, just before Judge Julius Hoffman sentenced him, he was offered a chance to speak. But when the judge tried to cut him off, Mr. Dellinger said: "You want us to be like good Germans, supporting the evils of our decade, and then when we refused to be good Germans and came to Chicago and demonstrated, now you want us to be like good Jews, going quietly and politely to the concentration camps while you and this court suppress freedom and the truth. And the fact is, I am not prepared to do that. You want us to stay in our place like black people were supposed to stay in their place. . . . "

His life took him a long way from his start in Wakefield, Mass., where he was an outstanding long-distance runner and high school athlete. He enrolled at Yale in 1933, during the depths of the Depression, and, embarrassed by the elitism he saw, spent vacations as a hobo, which he regarded as on-the-job training.

He graduated Yale as a Phi Beta Kappa economics major and won a scholarship to Oxford University. On his way to England, he slipped down to Spain, then into the middle of its civil war, and nearly defected from academia. But he went on to Oxford, then returned to Yale for graduate study and to the Union Theological Seminary to study for Congregationalist ministry.

Because protests did not pay the bills, Mr. Dellinger was a printer, writer and editor throughout his life. He was an editor of a series of small magazines -- Direct Action, Alternative, Individual Action and, finally, Liberation magazine, from 1956 until it closed in 1975. He wrote six books, the latest in 1993, "From Yale to Jail: The Life Story of a Moral Dissenter."

"Mainly, I think he'll be remembered as a pacifist who meant business," Hayden told the Associated Press. "His pacifism was very forceful. He didn't mind interjecting himself between armed federal marshals and someone they were pushing around."

Colman McCarthy, director of the Center for Teaching Peace Inc. in Washington, called Mr. Dellinger "truly a kind and lovable man, both a natural storyteller about all his decades of jamming the gears of the world's war machines, and an icon of nonviolence who taught that all of us are called to be peacemakers. In an era diseased with war, his arguments for pacifism remain bedrock-sound."

Survivors include his wife of 62 years, Elizabeth Peterson, and four children.

David Dellinger at home in Peacham, Vt., in 1985. He was best known as one of the Chicago Seven, arrested at the 1968 Democratic convention.