Lane Kirkland, 77, a labor statesman who was president of the AFL-CIO and was credited with uniting the nation's major unions at a time of rapidly changing economic conditions at home and abroad, died of lung cancer yesterday at his home in Washington.

Kirkland was a plain-spoken South Carolinian who served in the merchant marine in World War II. He spent his working life in the labor movement, joining the research department of the American Federation of Labor in 1948. He was a protege of the legendary George Meany, who became president of the AFL-CIO when it was formed in 1955 through the merger of the AFL with the Congress of Industrial Organizations. In 1979, Kirkland succeeded Meany in the top job.

In an interview shortly after he retired in 1995, Kirkland expressed his philosophy in these terms:

"The role of the trade unions is to try to keep big people from kicking around little people without a reaction. Your capacity to defend yourself is far greater if you're organized, if you do it as a union rather than as an individual."

President Clinton called Kirkland "a great American" -- always "ready and willing to serve his country." The president described him as a towering figure in the labor movement who was for nearly five decades "the guiding force for workplace fairness, innovation and a catalyst for international democracy."

Kirkland sought to put the principles he enunciated into action against increasingly difficult odds. In the mid-1960s, labor unions represented about 35 percent of the U.S. work force. By the mid-1990s, unions represented only about 15 percent of workers. Part of the reason was corporate downsizing. Part of it was the shift to a service economy, whose workers are difficult to organize. Still another part was the expanding global economy. Kirkland believed that the greatest threat to U.S. workers was low-paid foreign competition.

Labor felt besieged on the political front as well. Ronald Reagan's victory in the 1980 presidential election ushered in 12 years of Republican control of the White House, and Reagan's firing of striking federal air traffic controllers in 1981 set the tone for stronger measures against unions in the government as well as the corporate sector.

As an aide of Meany for two decades and then as president of the AFL-CIO, Kirkland was in the forefront of labor's efforts to meet these challenges. Part of the problem, he felt, was that some of the nation's most powerful unions were not part of the AFL-CIO. He set out to change that.

"All sinners belong in the church," he said.

By 1990, the United Steelworkers, the United Auto Workers and the Teamsters had all joined the fold, as had the West Coast Longshoremen, the Chemical Workers, the United Mine Workers and the Locomotive Engineers. In all, the AFL-CIO represented 78 unions with some 16 million members.

Kirkland also expressed views on a wide range of topics not directly related to unions. Like Meany, he was a passionate anti-communist and a supporter of U.S. involvement in the war in Southeast Asia.

In the early 1980s, he led the AFL-CIO in providing an estimated $6 million in aid to Solidarity, the Polish labor movement started by Lech Walesa that helped topple communism in that country.

He supported labor movements in many other countries. Within the AFL-CIO, he worked to promote women and minority members to high positions.

In a statement issued yesterday, John J. Sweeney, the president of the AFL-CIO, said, "American working families -- and workers around the world -- lost a warrior for the cause with the passing" of Kirkland. He described Kirkland as "one of the master builders of the modern American labor movement" and a "man of honor and principle who was steadfast in his beliefs and stalwart in his loyalties."

In 1994, President Clinton conferred the nation's highest civilian honor, the Medal of Freedom, on Kirkland.

Lane Joseph Kirkland was born March 12, 1922, in Camden, S.C. His father was Randolph Withers Kirkland, a cotton buyer. His mother was Louise Richardson Kirkland. His great-great-grandfather, Thomas Jefferson Withers, signed the Declaration of Secession that took South Carolina out of the Union at the beginning of the Civil War and later served in the Confederate Senate.

Lane Kirkland grew up in Newberry, S.C., a mill town, and it was there that he first became interested in the lot of the working man. Some of his classmates in high school worked in the mills after school, and the conditions under which they and their families lived excited his sympathy.

"They had company mill villages then," he told an interviewer. "If they'd fire a guy, he'd lose his house. He'd lose everything. There's no better way to get an education in becoming a liberal than to be exposed to those sorts of things."

With the outbreak of World War II, Kirkland tried to enlist in the Canadian armed forces. After he was turned down, he attended Newberry College. In 1940, he went to sea as a cadet in the U.S. Merchant Marine. When the U.S. Merchant Marine Academy opened, he became one of its first students. He graduated in 1942.

For the rest of the war, he served on merchant ships, rising to the rank of master. He joined the International Organization of Masters, Mates and Pilots, a move that provided him with his only direct experience as a rank-and-file union member.

After the war, he enrolled in the Georgetown University School of Foreign Service, from which he graduated in 1948.

He began his career with the AFL that year but also got an introduction to politics as a speechwriter for Alben W. Barkley, President Harry S. Truman's vice presidential running mate in the 1948 election. In the 1952 and 1956 elections, he wrote speeches for Adlai E. Stevenson, the Democratic nominee.

After the AFL-CIO merger, Kirkland was named associate director of its social security department. From 1958 to 1960, he was director of research and education of the International Union of Operating Engineers. He held that post until he became Meany's executive assistant in 1961. In 1969, he was elected secretary-treasurer of the AFL-CIO, the No. 2 job in the organization. The position made him Meany's heir apparent.

In the 1990s, Kirkland came under increasing criticism from members of the AFL-CIO executive committee who felt that he had not been aggressive enough in his efforts to stem the loss of union members. In 1995, he was persuaded to resign. He declined an offer from Clinton to become ambassador to Poland.

In retirement, he wrote and worked with young labor activists at the George Meany Center for Labor Studies.

Kirkland's marriage to the former Edith Draper Hollyday ended in divorce.

Survivors include his wife, the former Irena Neumann, and five daughters from his first marriage.