The last time Thomas Reid joined a civil rights demonstration, or any demonstration, for that matter, was in 1963, when he and a quarter million others marched here with Dr. Martin Luther King Jr.

But the 71-year-old retired postal worker was marching again last week in the rain because blacks in South Africa cannot vote or own land or enjoy any of the rights he now takes for granted.

"I think it's a rightful cause," said Reid, as he circled in a picket line with about 100 other apartheid demonstrators in what has become a weekday protest ritual at the South African embassy.

For Allison Green, 14, who was on the picket line a different afternoon last week, there is not that very personal sense of identification. She and her friends from an alternative high school in the District have been talking about South Africa in their science and social issues class -- and what she has heard has prompted her to strap on a "Free South Africa Now" sign and march with the others.

"I really dislike the idea of what's going on there," she said. "They're moving all the black people around and totally destroying townships where they've lived for years."

Since Nov. 21, when the Free South Africa Movement was launched with the arrests of Randall Robinson, executive director of the lobbying group TransAfrica, D.C. Del. Walter Fauntroy and U.S. Civil Rights Commission member Mary Frances Berry during a sit-in at the embassy, more than 200 persons have committed similar acts of civil disobedience. The protests and arrests have spread to Boston and Berkeley, and a dozen Eastern, Midwestern and Southern cities in between, and have involved prominent congressional, civil rights, religious and labor leaders as well as athletes and theatrical personalities.

Yet for every celebrity who goes to jail or holds a news conference denouncing apartheid and U.S. investments in South Africa, there are dozens of the not-so-famous who march and chant and provide a supportive presence.

In Washington and New York, where the largest number of demonstrators are seen each day, participants range from novices to protest veterans of the civil rights and antiwar era. They are of all ages, many races and several faiths. They are uniformly peaceful and collectively angry.

"We live in a country that supports a racist regime," said Susan Ellis, a 24-year-old law school student at American University, who has twice joined pickets in continuing protests a block south of the embassy's Massachusetts Avenue NW complex.

The Rev. Jerry Hargrove, chaplain for a graduate chapter of Alpha Phi Alpha, a black intercollegiate fraternity, said he hopes the antiapartheid struggle will result "not only in equality but equity" for South African blacks.

Some protesters, such as Nellie Shriver, 42, have come to the embassy picket line several times, distributing leaflets about what they see as related crusades. She is a member of the Boycott McDonald's Coalition, which claims that the hamburger chain is discriminating against blacks in the awarding of franchises in white areas.

Other demonstrators have brought children on the theory that youngsters are never too young to know about human rights.

"I was here before with two of my sons ages 9 and 10 ," said the Rev. Alan Chase, a Baptist minister and a recent arrival to the Washington area. "I want them to learn that part of being a citizen and being a Christian involves speaking out for what you believe."

Marquita Sykes, 39, took a day off from her job as a secretary and showed up at the embassy with members of her Black Women's Self-Help Collective.

"I guess I'm mainly here because it's organized," Sykes said as she picketed with a "Stop Apartheid Now" sign. "I don't know whether I came because of being a black person living in America or because I'm a human being. I guess they can't be separated." Allen Grooms, a regular presence at the embassy protest, remembers when members of the Ku Klux Klan attacked his home in North Carolina because his family included two Burmese foster brothers. Now 39 and a free-lance technical writer, he said he has been involved in the civil rights movement since the late '50s and in apartheid protests for the past 15 years.

"The issue of South Africa is not new," Grooms said. "It's a matter of having to be persistent."

The demonstrators in New York, where there have been daily protests at the South African consulate on Park Avenue, are no less committed to ending apartheid.

"I have to be here," said Robert A. Johnson, a 63-year-old military retiree from Harlem who arrives early every day, wearing a Martin Luther King Jr. button, an armed forces pin and a red ribbon to symbolize the bloodshed in South Africa. "It's urgent, a necessity. We've got to stamp out racism in our lifetime."

Estelle Crowly, 73, a gray-haired white woman from Manhattan, said she could not go to the demonstrations until last week because she was ill. "I'll keep participating until there's no need for it, for as long as I can walk," she said.

So far, the demonstrations in Washington, New York and other cities have been orderly and well orchestrated. As the Free South Africa Movement has taken hold, however, its organizers have had trouble keeping tabs on every activity and its outcome. There have been reports of antiapartheid arrests in Mobile, Ala., that never occurred and, sometimes, TransAfrica officials are the last to hear when a "spontaneous" demonstration occurs, such as those in Berkeley and San Francisco recently.

But in Washington, particularly, the protests have proceeded like clockwork. Amid the noise and supportive horn-honking of rush-hour traffic, organizers hold an afternoon news conference, introduce the "witnesses" scheduled for arrest that day and accompany them to police barricades. From there, a police officer escorts the demonstrators, usually no more than three, up the street to the embassy door. The protestors are arrested -- after two warnings -- when they refuse to leave the front of the embassy and, instead, sing verses of "We Shall Overcome."

D.C. police, many of whom are black and who work for a black chief and a black mayor who has hinted he may get arrested himself to fight apartheid, are especially patient and quietly supportive of the protests.

Fauntroy, cochairman of the Free South Africa Movement, is almost always there, marching, chanting and helping out. When organizers decided to break with the established pattern last Wednesday and allow a larger group to be arrested, for example, Fauntroy's car, driven by a protest organizer, was the lead vehicle in a three-car caravan up Massachusetts Avenue. The last two cars deposited additional demonstrators in front of the embassy.

Fauntroy also looks out for those whose protesting lands them in the D.C. Jail or other city holding cells. After the night he spent in incarceration, he raised a fuss about the cockroaches and dingy facilities. The place was soon fumigated and given a new paint job.

And when Evelyn Lowery, whose husband heads the Southern Christian Leadership Conference, encountered a "rude" corrections officer during her night in jail last Tuesday, Fauntroy said he complained to the agency and had it "deliver that person to me" so he could discuss the female employe's conduct.

Those who have spent the night in jail after their arrest at the embassy say the experience is no picnic, despite the obvious sympathy of law enforcement authorities. It takes a long time, they say, to process those arrested, even if they are not staying overnight, and the central cellblock is crowded with those who have been arrested for drug charges, urinating in the street or robbery.

"We had a surge of prisoners at 2 a.m., and they put a drunk driver in with us," said one local labor official who was sharing his cell Wednesday night with one other antiapartheid demonstrator. "It's crowded, and the lights are kept on all night, and there was one guy singing Christmas carols at 3 a.m."

But those memories were softened next day while he was waiting for arraignment.

"A marshal came over and took the five of us demonstrators who had spent the night in jail into a separate room," the labor leader recalled, smiling. "He brought us coffee and donuts and shook our hands and thanked us."