Bayard Rustin, 75, one of the great theorists and practitioners of the civil rights movement and a principal organizer of the great 1963 March on Washington, in which the Rev. Martin Luther King Jr. declared, "I have a dream," died yesterday at Lenox Hill Hospital in New York City after a heart attack.

He was hospitalized Friday and underwent surgery for acute appendicitis. He had complained of stomach pains after returning from a trip to Haiti.

Mr. Rustin was a socialist, a pacifist and a Quaker who had an unswerving belief in nonviolent protest as a way of bringing about social and economic progress for blacks and other minorities. Although he spent nearly half a century in the forefront of the civil rights struggle, he held many views that were unpopular with some influential blacks. For example, he opposed quotas in employment and education, which he thought were destructive to members of all groups.

"I am passionate that blacks should be able to make it like everyone else in this society," he said in an address at the Washington Hebrew Congregation in 1980. "I have not run into a single young black who wants something because he is black. He wants to pass the test and meet the standards."

He devoted his life to making it possible for blacks "to make it like everyone else," and in the process, he made a mark on most of the major milestones in that struggle.

In 1941, with the United States moving towards full participation in World War II, Mr. Rustin was youth organizer for a proposed march on Washington to force the government to open job opportunities for blacks in defense industries. Before the protest took place, President Franklin D. Roosevelt issued an executive order banning racial discrimination in all industries with government contracts.

During the war, Mr. Rustin spent 28 months in federal prisons as a conscientious objector. But he became field secretary of the Fellowship of Reconciliation, an organization devoted to promoting nonviolence as a solution to world problems, and in this role, he helped found the Congress of Racial Equality.

In 1947, he participated in a "freedom ride" in the South to demonstrate the effect of segregated public accommodations. Arrested in North Carolina, he spent 22 days on a chain gang. Two years later, an account of this experience that was published in a number of newspapers led to the abolition of chain gangs in North Carolina.

In the 1950s, Mr. Rustin became a close adviser to King and helped organize the Montgomery, Ala., bus boycott, the first of King's great undertakings. He also helped organize the Southern Christian Leadership Conference, and for seven years he was King's special assistant.

A longtime colleague of A. Philip Randolph, the head of the Sleeping Car Porters, he was the behind-the-scenes organizer of the 1963 March on Washington, of which Randolph was chairman. More than 200,000 people took part in the event and King gave the famous speech in which he declared, "I have a dream . . . . "

In 1964, Mr. Rustin organized a boycott to redress racial imbalance in New York City's public schools. It was held on Feb. 3 and 44.8 percent of the students participated. It was one of the largest civil rights demonstrations of any kind up to that time.

During the riots that ravaged Harlem in the summer of 1965, Mr. Rustin walked the streets in an effort to end the violence. Some blacks taunted him for being an "Uncle Tom" and he replied, "I'm prepared to be a 'Tom' if it's the only way I can save women and children from being shot down in the street."

In 1968, when garbage workers went on strike in Memphis, Mr. Rustin raised $100,000 to support them. When King was assassinated during the strike, Mr. Rustin organized a mass march in his honor.

In 1964, Mr. Rustin was named president of the newly organized A. Philip Randolph Institute, a clearinghouse for civil rights initiatives. He used this position as a platform to expound his view that civil rights had largely been secured to blacks and other minorities and that the focus of the struggle must be on economic and job opportunities.

Bayard Rustin was born in West Chester, Pa., on March 17, 1912. One of 12 children, he was reared by his grandparents. He was an honor student at West Chester High School and he was a member of the tennis track and football teams. When the football team went to Media, Pa., and he was ejected from a restaurant, he "took on the conviction that {he} would not accept segregation," he said in an interview.

He studied at Cheney State Teachers College in Pennsylvania and Wilberforce University in Ohio then went to New York, where he was a nightclub singer. He attended the City College of New York where he eventually graduated.

In 1936, he joined the Young Communist League. In 1941, disillusioned with communism, he left the league and joined the Fellowship of Reconciliation. Years later, some blacks criticized King for maintaining such close relations with Mr. Rustin and cited two grounds for criticism: his former communism and the fact that he was a homosexual.

On his release from federal prison at the end of World War II, Mr. Rustin became chairman of the Free India Committee and was arrested several times for conducting protests at the British Embassy in Washington. In the same period, he joined a committee that helped persuade President Harry S Truman to end segregation in the armed forces.

In the early 1950s, he helped found the Committee for Support of South African Resistance, and in 1953, he became executive secretary of the War Resisters League. In 1958, he went to Britain to help organize the Campaign for Nuclear Disarmament. In 1960, he protested French nuclear tests in the Sahara.

Although he became an elder statesman of the movement he had done so much to shape, Mr. Rustin never softened his principles. When he spoke at the Washington Hebrew Congregation in 1980, he went so far as to link the resurgence of the Ku Klux Klan to the "respectability" he said had been given to the Palestine Liberation Organization by such leaders as Andrew Young and Del. Walter E. Fauntroy (D-D.C.).

"You cannot give respectability to one terrorist group without other terrorist groups benefiting from that respectability," he said.

Mr. Rustin's survivors include three sisters, Adelaide Thomas of Coatsville, Pa., Ruth John of West Chester and Elizabeth Monroe of New York City.

JOHN DOYLE ELLIOTT, 80, a former lobbyist on Capitol Hill who had been a member of St. Luke's Episcopal Church in Bladensburg and senior citizens organizations, died of a heart ailment Aug. 23 at a nursing home in Seabrooke, Md. He lived in Seabrooke.

From 1947, when he moved here, until about two years ago, Mr. Elliott lobbied for the Townshend Plan, a social security scheme. He was a past director of the Bladensburg Senior Citizens and had been active with the National Council on Aging.

Mr. Elliott was a native of Philadelphia. He served in the Army in Europe during World War II. He earned a bachelor's degree at Harvard University and attended its law school.

His wife, the former Ruth Ellen Bowdey, died in 1981. Survivors include three stepsons, Adrian O'Connell of Palm Bay, Fla., Warren J. Neill of Albuquerque, and David Neill of Flourtown, Md., and two stepdaughters, Arlene Steffen of Hilton, N.Y., and Winifred Neill of Seabrooke.

GEORGE EDWIN DOW, 56, a vice president of Smith Barney Harris Upham Co., the stock brokerage, died Aug. 22 at the National Hospital for Orthopaedics and Rehabilitation in Arlington after a heart attack.

Mr. Dow, who was stricken at his home in Arlington, was born in Oakland. He moved to Washington about 1950 as a student at Georgetown University, where he graduated. He served in the Marine Corps in the early 1950s and then began a career as a stockbroker.

He worked for a number of firms, including Prudential Bache and Drexel Burnham, before joining Smith Barney in 1981.

He was a member of the Touchdown Club of Washington.

His marriage to the former Lydia Fenn ended in divorce.

Survivors include his wife, Anne Dow of Arlington; three children by his first marriage, Donna Kristoffersen of Vista, Calif., Mark Dow of Washington, and Brian Dow of Laguna Beach, Calif.; his mother, Velma Tesio Dow of Vista; one brother, Donald Dow of San Francisco, and two grandchildren.

LBERT J. HOSKINSON, 92, who served in the uniformed service of the U.S. Coast and Geodetic Survey for 36 years before retiring in 1957 as a captain, died of cardiac arrest Aug. 21 at the Carriage Hill nursing home in Silver Spring. He lived in Washington.

Capt. Hoskinson was an authority on tides and currents and helped design equipment used in astronomy and the study of gravity. He worked on geodetic and hydrographic projects throughout the United States, the Philippines and in the South Pacific.

He was a delegate to the 1954 meeting of the International Union of Geodesy and Geophysics in Rome. He served as chief of the survey's geodesy division before retiring.

Capt. Hoskinson, who moved here in the early 1950s, was a native of Kansas. He earned a bachelor's degree in civil engineering at the University of California at Berkeley. He served with the Army in World War I. In World War II, he was an instructor at the field artillery school at Fort Sill, Okla., and for this work he was awarded the Legion of Merit.

He was a member of the National Geographic Society. His hobbies included golf.

His wife, the former Marion A. McGham, died in 1974. Survivors include one sister, Isabel Felt of San Mateo, Calif.