Four years after the advent of black rule in Zimbabwe, the neat little octagonal Dutch Reformed Church in Harare functions openly, although a symbol to black Africans of white Afrikaner hegemony in South Africa.

"We have had no trouble at all," said Zacharias P. Le Roux, a young minister of the church on Samora Machel Avenue, in a recent interview.

"We have churches in all the major towns and cities of Zimbabwe. The government has allowed us to continue without any interference at all," Le Roux added.

This, and the fact that about 15,000 Afrikaners continue to live in this avowedly African socialist country, is testimony to a degree of mutual tolerance underlying the hostile rhetoric routinely exchanged between Pretoria and Harare.

There was a moment of anxiety last January when Zimbabwe's ceremonial president, the Rev. Canaan Banana, challenged the church publicly to denounce South Africa's segregationist doctrine known as apartheid.

As a minister of religion himself, Banana knew this would put the Afrikaner church on the spot. Not only does it give theological approval to apartheid in South Africa, it is itself racially segregated there into white, black, Colored (mixed-race) and Asian branches.

Because of this, the church was categorized as "heretical" by the World Alliance of Reformed Churches last year and suspended from the international body.

The church responded to the president's challenge by writing him a private letter, the text of which it has not disclosed. It has heard no more.

"We have in fact been given autonomy here in Zimbabwe and we have now desegregated," explained Francois Maritz, general secretary of the church's Central African Synod.

Maritz, 37, who was born in Zimbabwe, said he felt "very comfortable" under the black government and was "more at home" here than in South Africa, where he spent 10 years in theological school and as a minister.

But he admitted that he was "probably in the minority" among Zimbabwe's Afrikaners, many of whom have moved back to South Africa since Prime Minister Robert Mugabe's black majority government took over from the white colonists in 1980 after a long and bloody guerrilla war.

Many have been here for generations. The first came in ox wagons in 1893, brought by a pioneer named Duncan Moodie at a time when the British empire builder, Cecil John Rhodes, was opening up what he predicted would be an El Dorado colony that later was named Rhodesia.

Others followed, settling mainly on farms in the subtropical lowlands of the southeast, and on the high central and northwestern plains where the cattle ranching is good.

Maritz estimates that at their peak in the late 60s there were about 25,000 Afrikaners.

They adapted easily to the English ways of the colony and liked to think of themselves as less stiff-necked and more relaxed in their racial attitudes than their fellow Afrikaners "down south," according to Maritz.

But adapting to a black government proved more difficult. Conversations with some of them after the evening service in the Harare church on a recent Sunday revealed the anxieties many of them feel.

"I think our main worry is that we will lose our cultural identity as Afrikaners," said one who did not want to be named. "Many of us feel we have to submerge ourselves here."

The preservation of cultural identity is important to a community of 2.7 million whites who have been isolated and heavily outnumbered in a continent of more than 200 million blacks for more than three centuries. In South Africa it is the raison d'etre of apartheid.

Echoing the same concern, another churchgoer said that as ties with South Africa diminished, he worried about whether his children would grow up feeling themselves to be Afrikaners.

There used to be a special boarding school for Afrikaners outside Harare, called Bothashof, that was run by the Dutch Reformed Church.

The black government raised no objections to it continuing after independence, but it fell on hard times as the Afrikaners left. Within two years the number of pupils dwindled from 450 to 160, two headmasters quit to "go south" and the high school had to close.

Today Bothashof is still controlled by the church, but to survive it has had to be converted into an English-speaking school with an English headmaster and its doors open to all races.

Forsaking important cultural festivals is another worry. For example, Zimbabwe's Afrikaners have decided it would be imprudent to celebrate the most sacred of all their folk festivals, Geloftedag, in a black-ruled country. This is the anniversary of the Battle of Blood River, when the Afrikaner pioneers decimated the black Zulu army to avenge the killing of one of their leaders.

It falls on Dec. 16, and Rhodesian Afrikaners used to gather symbolically on the banks of the Bubye River in Matabeleleland Province to honor a vow of eternal gratitude made by their forefathers. A special speaker used to come up from South Africa.

Last Dec. 16 passed without even the token service in the Harare church that has been held in recent years.

"I actually forgot about it," Le Roux admitted shamefacedly.

Yet some Afrikaners are staying in a spirit of commitment that belies the general ethnic nervousness. One such is Francois Joubert, who farms near the small southeastern town of Chpinga, an area that was the hardest hit of all by Mugabe's guerrillas during the war.

More than 50 of the small local white community were killed. Joubert himself was ambushed by guerrillas twice and blown up once by a land mine.

His wife Ceylonia had their two children with her when their protected jeep hit a reinforced land mine and was shattered. Her heels were blown off and she is crippled. One of the children suffered serious skull injuries.

Ceylonia's brother-in-law was ambushed and killed. Her sister died soon afterward. They have adopted the couple's three children.

But despite their experiences, the family has no thought of leaving Zimbabwe, and Joubert is helping the government establish a black farming cooperative in the district.

"This is my home," Joubert said in an interview. "They couldn't shoot me out of it, so nobody's going to talk me out of it. There comes a time when you have to think positively and put the past behind you."

Bob van der Sande, who farms at Rutenga, west of Chpinga, is another Afrikaner who is determined to stay. He used to be farm manager for Ian Smith, the former rebel prime minister who tried to stop black majority rule by making a unilateral declaration of independence from Britain.

Van der Sande still admires Smith but he has come to terms with life under Mugabe. He has thought of moving to South Africa, but he is qualified only to farm and worries about what he would do for a living there.

"I would rather live like a white man here under a black government than like a black man there under a white government," he remarked.

At the other end of the spectrum is Jacobus Smith, an Afrikaner who went to extraordinary lengths to leave Zimbabwe when it "went black".

To beat the country's strict currency controls, Smith sold his two farms and a private plane, put the money into farm equipment, then slipped across the Limpopo River border into South Africa, hauling the equipment with him.

This he did by buying a farm on the South African side and renting one on the Zimbabwean side. Over three weeks during the dry season when the river was low, and with more than 100 clandestine crossings at night, he dragged everything from one side to the other.

Smith was armed as he made these crossings along with his three sons and son-in-law.

"I wasn't going to be arrested," he said when interviewed on his south bank farm. "If a white man had tried to stop me I'd have shot him in the leg.

"But if it had been a hout," he added, using a contemptuous Afrikaner word for blacks, "then I'd have just killed him."