Family members said McNamara died at his home in Northwest Washington. They did not give a cause of death.

McNamara was secretary of defense during the presidencies of John F. Kennedy and Lyndon Baines Johnson. In that capacity he directed a U.S. military buildup in Southeast Asia during the critical early years of a Vietnamese conflict that escalated into one of the most divisive and bitter wars in U.S. history. When the war was over, 58,000 Americans were dead and the national social fabric had been torn asunder.

Before taking office as secretary of defense in 1961, McNamara was president of Ford Motor Co. For 13 years after he left the Pentagon in 1968, he was president of the World Bank. He was a brilliant student, a compulsive worker and a skillful planner and organizer, whose manifest talents carried him from modest circumstances in California to the highest levels of the Washington power structure. He was said to have built a record of achievement and dedication in business, government and public service that few of his generation could match.

After his retirement from the bank in 1981, he maintained an exhausting schedule as director or consultant to scores of public and private organizations and was a virtual one-man think tank on nuclear arms issues.

But more than 40 years after the fact, he was remembered almost exclusively for his orchestration of U.S. prosecution of the war in Vietnam, a failed effort by the world's greatest superpower to prevent a communist takeover of a weak and corrupt ally. For his role in the war, McNamara was vilified by harsh and unforgiving critics, and his entire record was unalterably clouded. For the rest of his life, he would be haunted by the Vietnam ghosts.

From the day in 1961 when he burst upon the Washington scene as a political unknown selected by Kennedy to be secretary of defense, McNamara's trim figure, slicked-back hair and rimless glasses made him instantly recognizable, a Washington monument whose interests covered everything from nuclear war to the fiscal health of local governments.

At the Pentagon, he reorganized the military bureaucracy, built up the country's nuclear arsenal, and instigated a massive campaign to end racial discrimination in off-base housing. At the World Bank, he was often described as "the conscience of the West," for his relentless efforts to persuade the industrialized world to commit more capital to improving life in the have-not nations. In retirement, he avoided celebrity-for-hire appearances on the lecture circuit and the television talk shows, devoting his time and talent instead to improvement of education, government and health in this country and abroad and writing when he thought he had something to say.

He served as secretary of defense longer than anyone else, and in that role he was a key figure in such major crises as the Bay of Pigs fiasco and the Cuban missile confrontation with the Soviet Union. He changed the balance of nuclear forces in the world with the development of the multiple-warhead missile.

But his reputation foundered in Vietnam, a then-little-known country halfway around the world. Many Americans held him largely responsible for the futile and humiliating military adventure there--a responsibility he accepted in a controversial 1995 memoir of the war.

It was "McNamara's war," matching his technology, statistics, weaponry and organization charts against a peasant army from a small, impoverished country. The peasants won. In retrospect, it could be seen that McNamara's can-do, technological approach to military issues might have been perfectly suited to a conflict against the Soviet Union in Europe, but it led him into disastrous miscalculations in the jungles and paddies of Vietnam.

On his first visit to South Vietnam in 1962, before most Americans had heard of the place and before the involvement of American combat forces, McNamara said that "every quantitative measurement we have shows we're winning this war."