John Vorster, 67, a stocky, bushy-browed descendant of Dutch settlers who presided over the racially separatist policies of South Africa's white minority government for 12 years before internal scandal began to engulf his administration, died yesterday in Cape Town.

A lawyer whose forbidding visage seemed frequently set in a stern scowl, Mr. Vorster, the 13th child of a sheep farmer, served as prime minister from 1966 until his resignation in 1978.

The successor to the assassinated H. F. Verwoerd, the architect of South Africa's system of separate development of the races, Mr. Vorster was perhaps the first man to put the scheme into practice, with the granting of so-called independent status to two black areas.

As minister of justice in the 1960s, Mr. Vorster was known for ruthlessly repressive measures. As prime minister, he was regarded as a forceful advocate of his country's widely condemned policies of apartheid.

Yet, some students of South African affairs credit Mr. Vorster with also being the initiator, as prime minister, of a policy of pragmatic revisionism, which they say has in small ways improved the status of blacks, and has been extended by his successor, Pieter W. Botha.

Mr. Vorster's death came six days after he entered a Cape Town hospital suffering from a lung infection. It was his second hospitalization in a month for the same ailment. On Friday his personal physician said that his condition had deteriorated after a blood clot formed in one of his lungs.

The state of Mr. Vorster's health had been a matter of public interest five years ago, when he resigned as prime minister. Although he gave no immediate public reason for stepping down on Sept. 20, 1978, it was reported at the time that he was ill and had suffered a mild heart attack the previous month.

The next year, however, after Mr. Vorster had accepted the largely ceremonial post of president, a government report concluded that while prime minister he had been involved in illegal state funding of a multimillion-dollar propaganda drive in South Africa and abroad.

The report also concluded that he had tried to cover up financial irregularities in the secret project.

On June 4, 1979, amid news reports likening the scandal to Watergate, Mr. Vorster quit the presidency, with his career in public life severely tarnished. Only in the past few months had he begun again to speak out on public matters.

Although the scandal itself no longer appears to loom large on the international scene, it had considerable effect at home. It cracked the proud self-image of flawless probity and stern rectitude that had been cherished by the Afrikaners, the white descendents of Dutch settlers, who hold sway in South Africa.

Mr. Vorster, of Afrikaner descent, as are about 60 percent of South Africa's 4.5 million whites, was born on a farm in Jamestown in the northeastern part of Cape Province.

Growing up amid poverty, in a place and at a time where the whites of British descent held power, Mr. Vorster acquired early a strong sense of Afrikaner nationalism. After completing his secondary education in Strekstroom, he entered the University of Stellenbosch, where he took sociology and psychology courses from Verwoerd, who was to become his predecessor as prime minister.

Interest in politics and skill as a debater made him a leader among young members of the National Party, the present ruling party. He studied law, and in 1939 opened a practice in Port Elizabeth, the city where he later lived out his last years.

During World War II, he helped found a militantly anti-British, nationalist movement, was identified with extremist and authoritarian positions, opposed the Allied war effort and was interned for 20 months.

After the war, he resumed his political activity, winning a seat in Parliament in 1953, and taking a post in 1958 in the government of Verwoerd.

In 1961 he was appointed minister of justice. It was one year after the incident at Sharpeville in which police shot and killed more than 60 unarmed black demonstrators.

Mr. Vorster was implacable. "The rights of free speech, assembly and protest are getting out of hand," he declared. Measures were introduced giving the government the power to detain anyone for months without trial. More than 2,000 foes of apartheid were rounded up, and placed under what in many cases amounted to house arrest. Multiracial organizations were banned.

A ruthlessly efficient security apparatus was constructed. Its operation was beyond the scrutiny or control of courts, Parliament or the public.

On Sept 6, 1966, Verwoerd was fatally stabbed in the halls of Parliament by a deranged messenger whose motives were never clearly determined. Mr. Vorster was named his successor.

Adopting as his motto the words "fulfill your destiny," Mr. Vorster as prime minister appeared to forge ahead with his predecessor's policy of separate development for South Africa's approximately 19 million-member black majority.

The policy left blacks ineligible for South African political rights and required them instead to become citizens of the so-called "independent" ministates carved out of the South African territory.

It was a policy broadly condemned outside South Africa as denying blacks meaningful economic and political rights.

If Verwoerd conceived the policy, it was Mr. Vorster who began implementing it, giving "independent" status to the black areas of Transkei and Bophuthatswana. For years, no other country recognized them.

Whites in South Africa viewed Mr. Vorster's administration as bringing great change in blacks' status. His supporters indicated movement toward multiracial sports competitions and facilities, as well as the relaxation of discriminatory practices in major hotels and restaurants, and the granting of 99-year leases to black urban dwellers.

Critics said that these changes did no more than fray the edges of the monolithic structure of separate development, while skirting the basic issue of economic and political equality.

In 1974 Mr. Vorster began an effort to forge links with black-ruled states north of his country as a way to overcome the drift toward isolation. He held meetings with the presidents of three African nations, but South Africa's subsequent intervention in the 1975-76 Angolan civil war appeared to wilt Mr. Vorster's olive branch.

Internally, protests by blacks erupted in riots and demonstrations at Soweto in June, 1976, and continued over 16 months, resulting in at least 400 deaths. External reaction led to increasing international isolation.

Mr. Vorster, who preferred John to his given names of Balthazar Johannes, was married in 1941 to a fellow student at Stellenbosch University. He and his wife, Martini Malan, who was trained as a social worker, had a daughter and two sons.