Kwame Ture, who as Stokely Carmichael was a leading civil rights activist in the 1960s and used the slogan "Black power!" to rally blacks to the movement, died of prostate cancer Nov. 15 in Conakry, Guinea. He was 57.

Mr. Ture was a former president of the Student Nonviolent Coordinating Committee, a mainly 1960s civil rights organization. He also was a former prime minister of the Black Panther Party, the militant organization founded in Oakland, Calif., by Eldridge Cleaver, Huey P. Newton and Bobby Seale.

"He was one of our generation who was determined to give his life to transforming America and Africa," the Rev. Jesse Jackson said after hearing of his death. "He was committed to ending racial apartheid in our country. He helped bring those walls down."

A brilliant, charismatic and fearless agitator, Mr. Ture was introduced to civil rights activism in 1961 as a member of the famous Freedom Ride organized by the Congress of Racial Equality to desegregate interstate buses and bus terminals in the Deep South. This led to the first of the 30 or more arrests he suffered during the next several years.

He next became an organizer with the Student Nonviolent Coordinating Committee, whose first president was Marion Barry, later mayor of the District. In 1963, Mr. Ture led an SNCC voter registration drive in Lowndes County, Ala. -- then a segregationist and racist stronghold. The result of the drive was that registered black voters outnumbered registered white voters.

In 1966, he introduced "Black power!" to the nation's dialogue. He used the phrase at a rally in Greenville, Miss., after James Meredith, the first African American admitted to the University of Mississippi, was wounded by a sniper while leading a march. The effect of the slogan was electric; many blacks supported him and whites criticized him for reverse racism. The spread of the slogan and the message behind it were important factors in driving sympathetic whites from the ranks of the civil rights movement.

In 1968, Mr. Ture played an ambiguous role in the beginning of the riots that wracked Washington after the assassination of the Rev. Martin Luther King Jr. in Memphis on April 4. He led a crowd down 14th Street NW, ordering businesses to close. He tried to keep control of the marchers but looting broke out and fires were set.

The following day, he told a news conference, "White America will live to cry since she killed Dr. King last night." A short while later, he joined a rally at Howard University -- where he had been a student -- and waved a gun over his head and shouted, "Stay off the streets if you don't have a gun because there's going to be shooting."

It was his last public appearance in the riots, which included several days of curfew, thousands of Army, Marine Corps and National Guard troops, 10 deaths, 1,097 injuries, 900 fires and 6,124 arrests.

Mr. Ture was convinced that blacks would have to make their own destiny without white assistance. In 1967, his increasingly radical position led to his ouster from SNCC; in 1968, it ended his involvement with the Black Panther Party.

"The party has become dogmatic in its newly acquired ideology and thinks that it has the only correct position," he said in a public letter after his resignation. "The alliances being formed by the party are alliances which I cannot politically agree with because the history of Africans living in the United States has shown that any premature alliance with white radicals has led to complete submission of the blacks by the whites."

Mr. Ture moved to Guinea in 1968 and devoted the rest of his life to Pan-Africanism. He took the name Kwame Ture to honor Kwame Nkrumah, who led Ghana to independence from Britain, and Sekou Toure, who became president of Guinea after the end of French colonial rule. He turned to Marxism and supported communism even after it had been discredited in the Soviet Union and in other countries where it had formed the basis of government.

In a similar vein, Mr. Ture remained an admirer of Nkrumah and Toure, although both were widely criticized by their countrymen and international organizations for human rights violations. Nkrumah took refuge in Guinea after being ousted from Ghana and founded the All-African People's Revolutionary Party.

For years Mr. Ture made annual trips to the United States to discuss the party's program, mostly before university audiences.

The Pan-African program, he told audiences, was to become "one cohesive force to wage an unrelenting armed struggle against the white western empire for the liberation of our people." He condemned the United States, capitalism and Zionism.

In 1967, Mr. Ture and Charles V. Hamilton published "Black Power: The Politics of Liberation in America," in which they set forth a theoretical basis for the slogan.

"The concept of black power' rests on a fundamental premise: Before a group can enter the open society, it must first close ranks. By this we mean that group solidarity is necessary before a group can operate effectively from a bargaining position of strength in a pluralistic society. . . .

"The advocates of black power' reject the old slogans and meaningless rhetoric of previous years in the civil rights struggle. The language of yesterday is indeed irrelevant: progress, nonviolence, integration, fear of white backlash,' coalition."

This year while he was hospitalized for treatment of cancer, Mr. Ture was asked whether he thought that his calls for racial separatism and the rejection of passive resistance had contributed to the fracturing of the civil rights movement.

The question was unfair, he replied. "The knowledge I have now is not the knowledge I had then," he said. "I usually say I did the best I could with what I had. I have no major regrets."

As for fearful whites, he said, "The only thing they had to be frightened about was that Africans would break out of the space prescribed for them, and thus control of them would be far more difficult."

Stokely Carmichael was born in Port-of-Spain, Trinidad, British West Indies, on June 29, 1941. His father was Adolphus Carmichael, a carpenter, and his mother was Mabel F. Carmichael. In 1952, he moved to New York. The family lived in Harlem and later in Morris Park, a white section of the Bronx. He graduated from the elite Bronx High School of Science and went to Howard University, where in 1964 he received a degree in philosophy.

He was different from most of the leaders of the civil rights movement, who came from rural, southern backgrounds. Unlike them, he had had contact with whites for most of his early life. He was the only black member of the Morris Park Dukes, a neighborhood gang, and he went to schools where most of the students were white. He told an interviewer that he had even made "the Park Avenue scene."

None of this tempered his views. In 1967 he told the London Observer that as a boy in Trinidad he and his black schoolmates had gone to the movies "and yelled for Tarzan to beat the hell out of Africa."

"I'm angry because I didn't rebel," he said.

Mr. Ture's marriages to Miriam Makeba, the South African singer, and Marlyatou Barry, a physician in Guinea, ended in divorce.

Survivors include two sons, his mother and three sisters. CAPTION: KWAME TURE ec