When Randall Robinson, D.C. Del. Walter Fauntroy and U.S. Civil Rights Commissioner Mary Frances Berry held an antiapartheid sit-in inside the South African Embassy here last Thanksgiving Eve, they half expected, Robinson said later, that the ambassador would just call security guards and have them dumped unceremoniously off the premises.

Instead, the ambassador called police and had the three civil rights leaders arrested on trespassing charges. They spent the night in jail and emerged to announce plans for more demonstrations and the formation of the Free South Africa Movement.

Today, the antipartheid protest launched by those initial arrests marks its six-month anniversary. Riding a tide of support from expected and unexpected corners, the embassy protest and other demonstrations have moved South Africa's policies of racial separation and oppression from the back to the front burner of American consciousness.

Apartheid, a word not exactly on everyone's lips a year ago, has become the focus of wide media attention, congressional legislation, campus protests and Stevie Wonder songs.

There was even the recent withdrawal of South Africa's entrant in the Miss Universe contest. She cited antiapartheid political pressure and threats that weren't a concern at all a year ago when her predecessor won second place.

And, in the true test of whether a topic is catching on, apartheid and the demonstrations against it have recently captured the satiric attentions of the Doonesbury and Bloom County comic strips.

"We have been successful far beyond my wildest imaginings," Berry said yesterday. "When you start with almost zero interest in apartheid , which is what we started with, and then make it part of even the popular culture, that's really something."

Since Nov. 21, when the protests began, more than 3,180 demonstrators have been arrested nationwide, including 2,074 at the embassy, according to TransAfrica, the group spearheading the nationwide antiapartheid campaign.

Charges against most of the demonstrators, including all of those here, have been dropped. In Chicago, however, the jury trial of eight apartheid protesters ended in aquittal after the defendants argued that demonstrations at the South African consulate were necessary to prevent further racial oppression in South Africa. Protest organizers had long sought a courtroom forum to spotlight apartheid policies and U.S. support for the Pretoria government.

At yesterday's "Maryland Week" embassy demonstration, Fauntroy, Rep. Parren J. Mitchell (D-Md.) and about 70 church leaders and their families from Baltimore and Prince George's County picketed a block south of the embassy. Later, in what has become a familiar weekday afternoon scene along Massachusetts Avenue NW, six protesters crossed police lines and were arrested after singing "We Shall Overcome" directly in front of the embassy.

"We have been here every day of every week to say, 'Let My People Go,' " said Fauntroy, the cochairman of the Free South Africa Movement.

He asked the demonstrators to begin calling House members to urge support for proposed economic sanctions against South Africa, a legislative package on which Fauntroy said he and Mitchell would open floor debate today.

"This is just the first step," Fauntroy said.

"We will continue until no American corporation dares send money to South Africa and until no krugerrands are sold in the United States."

Krugerrands are gold coins minted in South Africa, and their sale has been another target of antiapartheid demonstrators, five of whom were recently arrested here after holding a two-day sit-in in the downtown offices of Deak-Perera, an international coin exchange firm.

Those charges, too, were dropped by the U.S. attorney.

Dick Ullrich, 46, whose group of Catholics from the Archdiocese of Baltimore has come to Washington four times to protest at the embassy, said apartheid always had been a concern of his.

"But it was the sit-in that kind of brought it to the street," he said. "That action said we had to do more than just talk about apartheid."

Yvonne Davis Robinson, whose husband, Anthony, was among those arrested yesterday, brought her two young children along to watch. "They need to know," she said.

The 24 weeks of protests have become a burden for organizers. "But it's picking up, and to the participants, it's still fresh and new," said Cecelie Counts, a TransAfrica staff member and a key organizer of the demonstrations. "It's beyond us to say that we'll stop at any given time."

Berry, a member of the Free South Africa Movement steering committee and one of the five persons arrested for the Deak-Perera sit-in, said the campaign has been personally exhausting.

"I never thought I'd be in Deak-Perera . . . lying on the floor in my nice suit, covered with newspapers, and be without water, food or going to the bathroom for 24 hours," she said.

"But what we have to go through is clearly not as arduous as what the folks in South Africa have to go through, so I'm proud to help."