Aaron Belkin, director of the Palm Center in California, a research institute at the University of California in Santa Barbara that studies issues surrounding gays and lesbians in the military, said that the vote “ushers in a new era in which the largest employer in the United States treats gays and lesbians like human beings.”

In a statement on the group’s website, Mr. Belkin said: “It has long been clear that there is no evidence that lifting the ban will undermine the military, and no reason to fear the transition to inclusive policy. Research shows that moving quickly is one of the keys to a successful transition. If the President and military leadership quickly certify the end of ‘don’t ask, don’t tell,’ they will ensure an orderly transition with minimal disruption."

Organizations that opposed repeal of the ban assailed the Republican senators who defied their party majority.

The Center for Military Readiness, a group that specializes in social issues in the military and has opposed repeal, said the new legislation “will impose heavy, unnecessary burdens on the backs of military men and women.” It said the Senate majority voted with “needless haste” by not waiting for hearings into a recent Department of Defense study of the “don’t ask, don’t tell” policy. Elaine Donnelly, president of the group, said that the Pentagon’s survey indicated that 32 percent of Marines and 21.4 percent of Army combat troops would leave the military sooner than planned if “don’t ask, don’t tell” were repealed.

Kris Mineau, president of the Massachusetts Family Institute, said senators like Scott Brown, a Republican from Massachusetts, “broke trust with the people” by voting on repeal before the federal budget was resolved and “have put the troops at risk during wartime.”

During the debate, Senator John McCain, Republican of Arizona and his party’s presidential candidate in 2008, led the opposition to the repeal and said the vote was a sad day in history. “I hope that when we pass this legislation that we will understand that we are doing great damage,” Mr. McCain said. “And we could possibly and probably, as the commandant of the Marine Corps said, and as I have been told by literally thousands of members of the military, harm the battle effectiveness vital to the survival of our young men and women in the military.”

He and other opponents of lifting the ban said the change could harm the unit cohesion that is essential to effective military operations, particularly in combat, and deter some Americans from enlisting or pursuing a career in the military. They noted that despite support for repealing the ban from Defense Secretary Robert M. Gates and Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, other military commanders have warned that changing the practice would prove disruptive.